School Chemistry: 200 Q&A for Classes 11-12, CUET, NEET, IIT

Q1:     

By heating aluminium, you can get chromium. Why?

A1:

Chromium cannot be produced using the carbon reduction process or the electrolytic process; therefore, it must be produced through the reduction of Cr₂O₃ with aluminium powder in a high temperature environment.

Q2:

H₂O₂ has a high dielectric constant but is never employed as a solvent. Why?

A2:

Because of its oxidising and reducing characteristics, H₂O₂ cannot be utilised as a solvent despite its very high dielectric constant.

Q3:

When placed in a solution of NH₄OH, CuSO₄ dissolves while FeSO₄ does not. Why?

A3:

In a solution of NH₄OH, CuSO₄ is soluble because it creates a complex molecule that is soluble when combined with NH₄OH. On the other hand, FeSO₄ does not generate this type of complex compound and is therefore insoluble.

CuSO₄ + 4NH4OH –> [Cu(NH₃)₄]SO₄ + 4H₂O

FeSO₄ + 2NH₄OH –> Fe(OH)₂ + (NH₄)₂SO₄

Q4:     

Both sodium and potassium are reactive elements, although potassium is more so. Why?

A4:

Potassium's ionisation potential is significantly lower than that of sodium. As a result, potassium is a more reactive element than sodium.

Q5:     

Comparatively, HF is a weaker acid than HI. Why?

A5:

The electro-negative properties of iodine are lower than those of fluorine. Thus bond between H-I is weaker than bonds between H-F. Hence, a greater amount of ionisation occurs when H-I is present in water as compared to HF. Thus, the acidity of HI is significantly higher than that of HF.

Q6:

If you had to define hybridization, what would you say it is?

A6:

Hybridization is the process of putting together different orbitals with almost the same amount of energy to make an equal number of new orbitals with the same amount of energy. Hybrid orbitals are the new orbitals that are made when two or more orbitals mix.

2s¹ + 2px¹ + 2py¹ + 2pz¹ –> four sp³ hybrid orbitals

Q7:     

To compare, Sodium is smaller than Potassium. Why?

A7:

Potassium is larger than sodium due to the fact that potassium possesses four orbits, whereas sodium only possesses three orbits (Na: 2, 8, 1; K: 2, 8, 8, 1).

Q8:     

Fluorine is less attracted to electrons than chlorine. Why?

A8:

Because fluorine has low dissociation energy and a high heat of hydration, its electron affinity is less than that of chlorine. The electron affinity is found using a Born-Haber cycle.

Q9:     

The oxidation number of oxygen is -2, while that of chlorine is -1. Why?

A9:

The most important oxidation number of a non-metal is its negative oxidation number, which is found by the formula below:

Negative oxidation number = Group number minus 8

Number of oxygen's oxidation = 6 minus 8 = -2

The chlorine oxidation number is 7 minus 8 = -1

Q10:   

The carbon-reduction process is used to make zinc. Why?

A10:

The carbon reduction process is used to get zinc because zinc oxide is easy to turn into zinc metal (Zn) when carbon is added.

Q11:   

Copper has a +1 and +2 valence. Tell me why.

A11:

Copper's electronic structure is 1s², 2s², 2p⁶, 3s² 3p⁶ 3d¹⁰, 4s¹. In copper, there isn't much difference between the energy of electrons in the outermost shell and those in the next inner shell. So, Cu has a valency of +1 because it lost an electron from 4s¹ and a valency of +2 because it lost an electron from 3d.

Q12:   

Why is the electrolytic process employed in the production of aluminium?

A12:

The utilization of the electrolytic process for aluminium production is attributed to the high stability of Al₂O₃. Due to this chemical stability, conventional chemical reduction methods are ineffective. Hence, the electrolytic reduction process is employed to successfully extract aluminium.

Q13:   

What does the Aufbau principle mean in the field of chemistry?

A13:

The Aufbau principle is one of the most important ideas in chemistry. It is also called the building-up theory. It tells how the electrons in an atom fill up the atomic orbitals. The Aufbau principle says that electrons fill the orbitals with the least energy first and then move to orbitals with more energy. This order of filling orbitals helps to explain how the elements in the periodic table are set up electronically.

When electrons are added to an atom, they move into orbitals in a certain order based on how much energy they have. The design shows the order of filling:

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d

This principle helps us understand how electrons are arranged inside atoms and shows us how the traits of elements change over time.

Q14:   

The cyanide technique is used to extract gold. Why?

A14:

Gold may be extracted from gold-bearing rocks using the cyanide method because gold can be dissolved out of gold-bearing rocks using NaCN solution in the presence of air, and gold can be pieces using zinc.

Q15:   

Why don't silver, gold, and platinum rust like iron does?

A15:

Unlike iron, noble metals such as silver, gold, and platinum do not undergo oxidation when they come into contact with oxygen in the air. This characteristic prevents them from experiencing the process of corrosion or rusting.

Q16:   

Radii of atoms or ions usually go down from right to left in a period. Why?

A16:

It is based on the fact that when you add more electrons, the electronic charge around the outside of an atom tends to get thicker instead of spreading out. Also, when a proton is added to the nucleus, the electron cloud tends to move closer to the nucleus. So, as we move from right to left, the size of the atom gets smaller.

Q17:   

CaF₂ doesn't mix with water. But it is a compound that has a charge. Why?

A17:

The lattice energy of CaF₂ is more than the hydration energy that it possesses. As a consequence of this, it does not ionise in aqueous solutions and it does not dissolve in water.

Q18:

The valence of the element with the 56th atomic number is...?

A18:

Specifically, the element has the electrical configuration 1s²; 2s²2p⁶; 3s²3p⁶3d¹⁰; 4s²4p⁶4d¹⁰; 5s²5p⁶; 6s². The valence of the element is 2, as the outermost orbit contains two electrons.

Q19:

In your own words, please explain what nuclear fusion is.

A19:

Nuclear fusion happens when two light atomic nuclei join together to make a single, heavy nucleus. This is a normal process that happens inside stars, including the Sun, and it gives off a lot of energy.

For decades, scientists have been trying to figure out how to use fusion energy on Earth to make things like power. The goal is to get clean, safe, and renewable energy.

Scientists and engineers have been looking into how to make nuclear fusion happen on Earth and use it on a large scale.

Fusion fuel has many advantages such as being a completely renewable, clean, safe, and cheap source of energy. Fusion can make about four times as much energy per kilogramme as fission, and it can make almost four million times as much ‘energy’ as burning coal or oil.

Many of the ideas for fusion reactors that are currently being worked on will use deuterium and tritium, which are hydrogen atoms with extra neutrons that can make a terajoule of energy from just a few grammes. This is enough energy to power one person in a developed country for sixty years.

Another good thing about fusion is how easy it is to get the raw materials. Deuterium can be taken out of saltwater, and tritium can be made when neutrons and lithium react. Both of these products will be around for a very long time.

Fusion has the ability to provide almost unlimited clean energy, and it is also a safe source of energy that doesn't make long-lasting nuclear waste like fission does. Because it is hard to start and keep a fusion reaction going, there is no chance that the reaction will get out of control and cause a breakdown. In the event of an accident, the plasma will end and lose all of its energy very quickly, before the reactor takes any long-term damage.

Lastly, fusion doesn't put any carbon dioxide or other damaging greenhouse gases into the air. This makes it a source of low-carbon energy as well.

Q20:

What exactly is the definition of a real gas?

A20:

A real gas is one that can't be described by the gas equation V=RT. In other words, a real gas is one for which the gas equation V=RT does not hold. In real gases, the actual volume filled by gas molecules and the forces of attraction between them are taken into account.

Q21:

Tell me about neutrons. What led to its discovery?

A21:

Neutrons are particles in the center of an atom that have no electrical charge. In 1932, Chadwick found the third fundamental particle by splitting the nuclei of some light elements (like beryllium) with fast alpha (α) particles. This basic particle was called a neutron.

Q22:

What is the definition of orbital?

A22:

Orbital is the space around the center of an atom where the electron is most likely to be found. The form of the orbitals is determined by plotting the electronic wave function  of an electron. Because of this, the orbitals are called s, p, d, f, etc.

Q23:

Copper sulphate in water forms an acidic solution. Why?

A23:

A solution of CuSO₄ in water that has been broken down by water is acidic. The theory of ionisation can be used to explain the hydrolysis.

CuSO₄ <=> Cu⁺⁺ + SO₄^--

2H₂O <=> 2H⁺ + 2OH^-

Cu⁺⁺ + 2OH^- –> Cu(OH)₂

2H⁺ + SO₄^-- –> H₂SO₄

Because H₂SO₄ forms, which is a strong acid, there will be too many H⁺ ions, making the water solution acidic.

Q24:

The Pauli Exclusion Principle is defined as what?

A24:

“Four quantum numbers can't be the same for two electrons in an atom”. So, this principle put a limit on how electrons can act. No two electrons in an atom will have the same four quantum numbers, so they can't act the same way.

Q25:

What exactly is the Hund rule?

A25:

“The electrons are arranged within the orbitals in such a way that there are a maximum number of unpaired electrons that have the same spin direction in each orbital”.

Q26:   

Why are both the atomic number and the valency represented by whole numbers?

A26:

The atomic number represents the count of protons within an atom's nucleus, making it a whole number since protons are indivisible particles.

Valency, which indicates an atom's capacity to combine with other elements, is also expressed as a whole number. It represents the number of hydrogen atoms an element's atom can bond with. Since atoms cannot form partial bonds, the valency is always a whole integer.

Q27:    

Why does liquid NaCl conduct electricity, while anhydrous HCl does not?

A27:

Liquid NaCl conducts electricity due to its ionic nature as an electrovalent compound. In contrast, anhydrous HCl does not conduct electricity because it is a covalent compound and does not dissociate into ions in its anhydrous form.

Q28:    

When you say "isotopes", what exactly do you mean?

A28:

Isotopes are a fascinating aspect of the natural world, composed of atoms – the tiniest units of matter, each possessing the full spectrum of chemical characteristics inherent to an element. Isotopes represent distinct variations of a chemical element, each exhibiting unique properties.

Unveiling the Periodic Table's Mysteries

The periodic table offers a visual feast of various chemical elements, each occupying its designated spot. This table serves as a treasure trove of information, revealing the identity of each element based on its protons, neutrons, and electrons.

The Intricacies of Atomic Composition

In the realm of atomic structure, protons and electrons are constants, their quantities unchanging for a given element. Neutrons, on the other hand, introduce variability to the equation. Isotopes come into play when atoms possess identical proton counts but differ in their neutron content.

Diving into Isotopic Properties

Isotopes exhibit uncanny similarities in chemical behavior while boasting diverse physical properties due to differences in mass. This diversity is highlighted by the distinction between stable isotopes, which lack radiation emission, and unstable counterparts, known as radioisotopes, that emit radiation.

A Glimpse into Isotopic Facts

Let's dive into some quick and intriguing facts about isotopes:

• Isotopes are omnipresent within all known elements.
• Isotopes divide neatly into two primary categories: stable and unstable (or radioactive).
• The roster of stable isotopes boasts a total of 254 well-known members.
• Synthetic isotopes, born within laboratories, universally bear an unstable, radioactive nature, thus earning the title "radioisotopes."
• Certain elements, like uranium, exclusively exist in an unstable state.
• Notably, hydrogen's isotopes wear distinct monikers: "deuterium" for the variant with one neutron and "tritium" for the iteration containing two neutrons.

Through this illuminating journey, we've uncovered the realm of isotopes, their variegated properties, and their significant role in the intricate dance of elemental composition.

Q29:   

Carbon is a non-metal, whereas lead is a metallic element. Why?

A29:

On the periodic table, carbon and lead are both assigned to the same group: group IV A. According to what we know, the proportion of elements in a subgroup of the periodic table that are metallic or electropositive rises as the number of their constituent atoms rises. Lead is the only element in this subgroup that is a metal. The other elements in this subgroup are all non-metals.

Q30:   

When heated, copper sulphate, which is normally 'blue’, becomes ‘white’. Why?

A30:

Blue copper sulphate is wet, and it has five water molecules in it. When heated, it turns into anhydrous copper sulphate, which is white.

CuSO₄.5H₂O (blue copper sulphate, when heated) –> CuSO₄ + 5H₂O (becomes white in colour)

Q31:   

Although having a very high dielectric constant, H₂O₂ is never used in the role of a solvent.

A31:

H₂O₂ has both oxidising and reducing properties, so even though it has a very high dielectric constant, it can't be used as a solvent. A solvent must not have either oxidising or reducing properties.

Q32:

Exactly what does "group displacement law" mean?

A32:

Group displacement law says that if an element gives off an alpha particle, the new element that is made has a number that is four less than the original element and is in a group that is two columns to the left of the original element on the periodic table. In a beta-particle, the new element has the same mass as its parent, but it is one column to the right of it.

Q33:   

The carbon reduction process makes zinc. Why?

A33:

The carbon reduction process is used to get zinc because zinc oxide is easy to turn into zinc metal when carbon is added.

ZnO + C –> Zn + CO

Q34:   

The level of reactivity of zinc dust is higher than that of zinc granules. Why?

A34:

Zinc dust has a significantly higher surface area compared to zinc granules. Granules, on the other hand, need some energy in order to react with zinc dust.

Q35:

Nitrogen has more than one valency. Please elaborate briefly.

A35:

The electronic configuration of an atom of nitrogen is 1s², 2s², 2p³. It goes through two stages of electron loss. In a chemical reaction, nitrogen first loses the three electrons in its 2p orbitals, and then it potentially loses the two electrons in its 2s orbitals. Hence, it demonstrates the valency of +3 and +5 respectively.

Q36:   

When lead nitrate is heated, it releases a pale yellow gas that, when heated very strongly, turns a dark brown colour. Why?

A36:

After being heated, lead nitrate initially decomposes into N₂O₄, a gas that has a light yellow colour; after being heated even further, N₂O₄ is transformed into NO₂, which has a dark brown colour.

Q37:    

Unraveling the Enigma of Electrons: What exactly is an electron?

A37:

An electron stands as a remarkable particle, bearing a negative charge and possessing a mass equivalent to 9.1083 x 10^-31 kilograms. This minute entity is graced with a unit of negative charge, a fundamental characteristic that defines its intriguing nature.

Q38:   

Cuprous hydroxide, which has the formula Cu(OH)₂, dissolves in ammonium hydroxide but not in a solution of NaOH. Why?

A38:

Cuprous hydroxide can dissolve in ammonia because it forms a soluble complex called cupra ammonium hydroxide.

Cu(OH)₂  + 4NH₄OH –> [Cu(NH₃)₄](OH)₂ + 4H₂O

On the other hand, Cu(OH)₂ does not form complexes when it reacts with sodium hydroxide.

Q39:   

Light bulbs that use flash lighting depend on magnesium. Why?

A39:

When combined with oxygen, magnesium creates a bright glow, that's why we find it in flash bulbs.

Q40:   

Unlike PH₃, NH₃ dissolves in water. Why?

A40:

The chemical NH₃ is polar, just like water. Because it is a polar compound, water can dissolve it, but because PH₃ is a non-polar compound, water cannot dissolve it.

Q41:

How do you define alpha, beta, and gamma rays?

A41:

Aalpha rays are made up of particles with two positive charges and the same amount of mass as an atom of helium (He). Their speed is about one-tenth of the speed of light. Beta rays are negatively charged particles that move quickly and have the same mass and charge as electrons. Gamma rays are very short-wavelength electromagnetic waves. Gamma rays don't have any charge, but they move as fast as light. It can get into things very well.

Q42:    

“Demystifying the Proton - Nature's Positive Charge”: What exactly is a proton?

A42:

At the heart of atomic intricacies lies the proton – a particle of significant positivity. Its mass, quantified at 1.672 x 10^-27 kilograms, is complemented by a single unit of positive charge, rendering it a cornerstone of fundamental particles.

Q43:    

"Unveiling Hydrogen Bonding: A Force of Nature": Hydrogen bonding, what is it?

A43:

Hydrogen bonding, an intriguing phenomenon in the realm of molecular interactions, comes to life when an electronegative atom and a hydrogen atom already bonded to another electronegative partner come together. This unique alliance forms what we recognize as a hydrogen bond – an attractive force rooted in dipole-dipole interactions.

The Dance of Hydrogen Atoms

At the core of hydrogen bonding lies the involvement of a hydrogen atom. These bonds transcend molecular boundaries, weaving connections between diverse molecules and even different segments of the same molecule.

Balancing Act: Strength and Composition

Hydrogen bonds possess a distinct strength, surpassing the feeble grasp of van der Waals forces. Yet, they fall short of the resilience demonstrated by covalent and ionic bonds. Their strength is approximately a mere 5% of the covalent bond's potency, the bond formed between oxygen and hydrogen.

Seeking the Third Connection

But why would a hydrogen atom seek to forge a third connection when already bound to another? The answer lies in the polarity of bonds. Even in a polar bond, a slight positive charge persists on one side while its counterpart carries a subtle negative charge. Despite bonding, the electrical attributes of atoms remain unchanged.

Hydrogen Bonds: From Nucleic Acids to Water Molecules

In the intricate tapestry of molecular interactions, hydrogen bonds play pivotal roles, especially in nucleic acids. Here, they link base pairs and water molecules, steering the course of intricate biochemical processes.

Through hydrogen bonding, nature orchestrates delicate forces that shape molecular landscapes and influence the behaviour of atoms and molecules alike.

Q44:    

"Decoding Sodium Production: A Molten Mystery": Sodium is made by electrolyzing molten sodium chloride. It is not made by electrolyzing its solution in water. Why?

A44:

The enigma of sodium production finds its answer in the realm of electrolysis. Electrolyzing an aqueous solution of sodium chloride does not yield sodium, contrary to popular belief. Instead, the cathode breathes life into hydrogen gas, unveiling a scientific truth – sodium remains elusive.

Unraveling Electrolysis's Secret Dance

When sodium chloride takes the form of an aqueous solution, the electrolysis process unveils an unexpected guest: hydrogen gas. This phenomenon unfolds at the cathode, where hydrogen gas is liberated, leaving sodium in the shadows.

In contrast, when sodium chloride embraces its molten state, electrolysis becomes a creative force that yields sodium. The molten sodium chloride surrenders its essence, bestowing sodium with the chance to emerge as the result.

The Hydrogen Intrigue

At the heart of this narrative lies the cathode's role. In the presence of water, this electrode orchestrates the release of hydrogen gas, eclipsing the possibility of sodium formation. This revelation is a testament to the intricate dance between elements and the fascinating outcomes that emerge from controlled reactions.

Through the lens of electrolysis, we come to understand that sodium's origins are inherently tied to the state of its bonding partners – a molten alliance that begets the coveted metal, steering clear of hydrogen's allure.

Q45:

What does mass number mean?

A45:

Mass number is the total number of protons and neutrons in an atom's core. The mass number of sodium is 23, for example, because its nucleus has 11 protons and 12 neutrons. The number for mass is a whole number and is very close to the number for atomic weight.

Q46:    

"Unveiling the Interplay Between Zinc and Copper: The Mystery of Precipitation": When zinc metal is introduced to a copper sulphate solution, copper precipitates. What's the reason behind this phenomenon?

A46:

The captivating chemistry that unfolds when zinc and copper sulphate join forces leads to the intriguing precipitation of copper. The question that naturally arises is: why does this fascinating transformation take place?

The Symphony of Reactivity

Enter the electrochemical series, a hierarchical arrangement of elements based on their reactivity levels. Here, zinc takes a commanding position above hydrogen, indicating its higher reactivity. Below hydrogen, we find copper, positioned slightly lower. This arrangement sets the stage for the dynamic interplay between these two elements.

Unravelling Reactivity

Upon the introduction of zinc, the more reactive participant, to the copper sulphate solution, an intricate exchange of electrons and ions ensues. Driven by its greater reactivity, zinc seeks to forge equilibrium with copper. This orchestrated exchange results in the precipitation of copper, as the comparatively less reactive copper surrenders its place to the more reactive zinc.

A Tale of Chemical Choices

In this delicate dance of reactivity, the less reactive copper sulphate yields to the commanding influence of zinc. The outcome is an enchanting display of copper precipitation. This captivating occurrence highlights the profound connection between an element's reactivity and its role within the intricate tapestry of chemical reactions.

Through this compelling narrative, we witness the captivating interaction between zinc and copper sulphate, unravelling the secrets of elemental dynamics and the mesmerizing chemistry that guides their path.

Q47:    

"The Essence of Metallic Bonds Unveiled": In simple terms, what exactly is a metallic bond?

A47:

Metallic bonds encompass the captivating forces that link positive metal ions to the valence electrons in perpetual motion around them. This interplay involves the continuous movement of valence electrons, which not only belong to the ions themselves but also to nearby ions of the same metal.

Dynamic Dance of Electrons

At the heart of a metallic bond is the intricate dance of valence electrons – those elusive particles that define an element's chemical behaviour. These valence electrons flow freely due to metals' comparably low electronegativity, or attraction to electrons. This unfettered flow is facilitated by the metals' inherent low electronegativity.

The Artistry of Metal Ions

A metallic bond's canvas is painted by the arrangement of positive metal ions. These ions create an artistic lattice-like structure, interconnected through the symphony of metallic bonds. This arrangement stands as a testament to the collective forces holding the lattice together.

Metal and Non-Metal Divide

The unique allure of metallic bonds is exclusive to metal elements, and for a good reason. Metal atoms willingly relinquish their valence electrons to become positive ions, laying the foundation for this distinctive bond. On the other hand, non-metal atoms share valence electrons in chemical connections, resulting in covalent bonds that preclude the formation of metallic bonds.

For instance, the union of two oxygen atoms results in an oxygen molecule where valence electrons are shared evenly between the atoms. This contrast between metal and non-metal behaviour underscores the beauty of the periodic table's diversity and the bonds that bind elements together.

Q48:   

Copper can be broken down by HNO₃, but not by HCl. Why?

A48:

The oxidising capacity of HNO₃ is significantly higher than that of hydrochloric acid. Because of this, HNO₃ is capable of easily oxidising copper to form Cu(NO₃)₂ which is a compound that can be dissolved in water.

Q49:   

When looking at a set of P.T. values, the melting and boiling points of a metal get lower as we move from top to bottom, whereas the values for non-metals get higher. Why?

A49:

Because the size of the atoms rises from top to bottom in a metal, the lattice energy of the metal often decreases as one move from the top to the bottom. When the lattice energy of a metal is higher, both its melting point and its boiling point will also be higher. Hence, the point at which metals melt and boil lowers as they move from the top to the bottom of the container.

For a given group in P. T., the non-metal compounds with the highest lattice energy are found at the top. Hence, moving from the top to the bottom of a group consisting of non-metals typically results in an increase in melting and boiling points.

Q50:   

Why are metals referred to as electro-positive elements?

A50:

In order to complete their octets, metals frequently give up electrons, resulting in the formation of positive ions. This is why these elements are classified as "electro-positive".

Na (11) –> Na (10)                 [Give up electron]

(2, 8, 1)      (2, 8)

Q51:   

Nitric acid that is very strong and concentrated can be put in containers made of aluminium. Why?

A51:

Due to the creation of a protective coating of aluminium oxide on aluminium, it is possible to store highly concentrated HNO₃ in aluminium containers. This allows for the container to be made of aluminium (Al₂O₃).

Q52:   

The term "electro-negative element" is used to describe materials that are not metals. Why?

A52:

In order to fully complete their octets, non-metals frequently take on additional electrons, which results in the formation of negative ions. Because of this, we refer to these elements as electro-negative.

Q53:   

When N₂ is oxidised by O₂ in the presence of H₂O, it forms nitrate ions, which is bad for thermodynamics. However we do not get oceans of dilute HNO₃ in nature. Why?

A53:

Thermodynamically, the following reactions are possible with N₂ and O₂ in the presence of H₂O.

N₂ + O₂ –> 2NO

2NO + O₂ –> 2NO₂

H₂O + 2NO₂ –> HNO₃ + HNO₂

3HNO₂ –> NO₃ + 2NO + H₂O

The first step of the above reaction is temperature dependent, so a higher temperature, like 300^oC, is needed. Only lightning does this, which doesn't happen very often. So, the environment does not have an ocean of HNO₃.

Q54:   

In its acidic state, HCl shows electro-valency, while in its gaseous form, it is a polar covalent. Why?

A54:

The bond between hydrogen and chlorine is covalent, but when dissolved in water, the more electronegative chlorine atom pulls the shared pair of electrons towards itself, giving hydrogen a partial positive charge and chlorine a partial negative charge. So, covalency changed into electrovalence in a solution.

Q55:

How do you define a quantum number?

A55:

Quantum numbers are numbers that are used to describe where an electron's energy is. Also, they decide the size, form, and orientation of the orbital to which the electron belongs. They are:

(1) Principal quantum number (n),

(2) Azimuthal quantum number (i),

(3) Magnetic quantum number (m),

(4) Spin quantum number (s).

Q56:   

Water dissolves noble gases more easily than oxygen does. Why?

A56:

The polarizability of the noble gases with large atoms is greater than that of oxygen. Hence, the noble gases dissolve more easily in water compared to oxygen. Dipole-induced dipole interaction is responsible for the solubility of the compound.

Q57:   

During electrolysis, metals are deposited on the cathode. Why?

A57:

In general, metals tend to lose electrons and turn into positive ions. Because of this, they are freed during cathode electrolysis.

Q58:    

"Unveiling the Ozone Mystery in the Upper Atmosphere": The upper atmosphere is where ozone can be found. Why?

A58:

The captivating presence of ozone unfolds its tale in the upper reaches of our atmosphere, and the underlying reason is rooted in a transformative interplay of oxygen and ultraviolet rays.

A Symphony of Transformation

Ozone, a trio of oxygen molecules united in a unique arrangement, emerges through a process sparked by ultraviolet rays. When oxygen encounters these energetic rays, a fascinating metamorphosis occurs, leading to the birth of ozone. This transformation primarily unfolds in the upper echelons of our atmospheric expanse.

Where Rays Dance

The upper atmospheric layers prove to be a hotbed for ultraviolet rays, serving as the stage for this remarkable interaction. These rays, emitted by the sun, permeate this altitude with their energetic presence, catalysing the conversion of oxygen into ozone.

A Cosmic Choreography

The reason behind ozone's upper-atmospheric residence is intricately linked to the cosmic choreography of sunlight, oxygen, and ultraviolet rays. The upper layers provide the ideal milieu where ultraviolet rays are prevalent, propelling the creation of ozone and fostering the remarkable balance that characterizes Earth's atmospheric layers.

As we peer upwards to the heavens, we find the upper atmosphere abuzz with the symphony of ozone's formation – a reminder of the intricate interplay between elements and energy that shapes our planet's protective shield.

Q59:   

In the halogen family, iodine is a solid. Why?

A59:

As the number of atoms in a group of halogens goes up, the number of electrons also goes up. This makes the Vander Waal more attractive, and it is at its most attractive in iodine. As Vander Waal's attraction gets stronger, the distance between atoms gets smaller. So iodine is solid.

Q60:   

The solubility of pure iodine in CCl₄ is higher than that in water. Why?

A60:

Iodine is a covalent chemical, and because CCl₄ is also a covalent compound, it is easier for it to dissolve in CCl₄ than it is in water, which is a polar covalent compound.

Q61:    

Unveiling the Enigma of "Dry Ice": Dry ice refers to solid carbon dioxide. Why?

A61:

"Dry ice" finds its unique name from the intriguing characteristic that sets it apart. Solid carbon dioxide, when it transitions from its solid state to a gaseous form, doesn't undergo the conventional melting process. This unusual behaviour of carbon dioxide gives rise to the moniker "dry ice."

Q62:   

If we put a piece of blue litmus paper into a solution of hypochlorous acid, the paper will turn red and then become oxidised. Why?

A62:

Because of its instability, hypochlorous acid breaks down into:

HOCl –> HCl + O

The red colour of litmus paper that formed in the presence of HCl is bleached by the newly formed oxygen.

Blue Litmus + HCl –> Red Litmus + O –> Colourless Litmus

Q63:   

Hydrolysis occurs for SiCl₄ but not for CCl₄. Why?

A63:

In SiCl₄, Si has an empty d-orbital, but C does not have an empty d-orbital in CCl₄. So, SiCl₄ is broken down by water by putting lone electron pairs in d-orbitals.

SiCl₄ + 4H₂O –> Si(OH)₄ + 4HCl

Si(OH)₄ –> SiO₂ + 2H₂O

Q64:   

Hydrogen peroxide has both reductive and oxidising properties. Why?

A64:

It gives off oxygen easily and is therefore an oxidising agent.

H₂O₂ –> H₂O + O

Since it is easy to combine with oxygen, it acts as a reducing agent.

H₂O₂ + O –> H₂O + O₂

Q65:    

"Unravelling the Electro-Negative Dominance: Chlorine vs. Bromine": When compared to bromine, the electro-negative nature of chlorine is greater. Why?

A65:

The captivating contrast between chlorine and bromine's electronegativity is rooted in the intricate dance of electronic configurations. Let's delve into the heart of this phenomenon:

Unveiling Electronic Arrangements

Chlorine (Cl) bears an electronic configuration of 1s², 2s² 2p⁶, 3s² 3p⁵, whereas bromine (Br) boasts a configuration of 1s², 2s² 2p⁶, 3s² 3p⁶ 3d¹⁰, 4s² 4p⁵. Although both elements find their place in Group VII of the periodic table, chlorine occupies the third period while bromine resides in the fourth.

The Influence of Periodic Trends

The periodic table holds the key to unravelling this electronegative enigma. As elements progress down a group, the electronegativity experiences a decline. Herein lies the answer to the puzzle: chlorine's position in the third period grants it a stronger negative charge compared to bromine, positioned in the fourth period.

An Electronegative Duel

In this dynamic duel of electronegativity, chlorine emerges as the victor due to its third-period residency. This intriguing phenomenon underscores the influence of periodic trends on the electronegative forces that define an element's behaviour.

As we explore the periodic table's intricacies, we uncover the captivating forces that shape elemental characteristics and provide insights into the unique attributes that set them apart.

Q66:

H₂O₂ has a higher acidity level than water. Why?

A66:

H₂O₂ and water are both very mild acids. Since they are oxy acids, their potency can be calculated as follows:

Potency (strength) = (the electrical charge that is carried by the acid ion) / (The number of oxygen atoms that are present in their acid)

H₂O;    O^-2;      2/1 = 2

H₂O₂;  O^-2;      2/2 = 1

The acidity increases as the ratio decreases. Hence, H₂O₂ is more potent than H₂O.

Q67:

Exactly why aren't there any molecules like H₃ and H₄?

A67:

The overlap of orbitals was the driving force behind the creation of H₂ molecules. This indicates that both of the electrons that were accessible during the creation of the covalent bond have been spent. There are no free electrons left behind at this point. There is no possibility for additional hydrogen atoms to form bonds with H₂ molecules. As a result, there is only H₂, while H₃ and H₄ do not exist.

Q68:

Electricity can be conducted through molten ionic liquids, but not through ionic solids. Why?

A68:

While the substance is in a molten condition, the ions are free to move about, which allows electricity to flow. Ionic solids, on the other hand, do not allow ions to freely flow within the crystals, which is another reason why they do not conduct electricity.

Q69:    

"Unravelling the Pre-Electrolysis Ritual: The Role of Acid and Alkali": Adding a small amount of acid or alkali prior to water electrolysis is common practice. Why?

A69:

The intriguing practice of introducing a dash of acid or alkali before initiating water electrolysis finds its purpose in transforming water's conductivity. This transformation is at the core of this ritual:

Catalysing Conductivity

When a modest quantity of acid or alkali is infused into water, a magical metamorphosis takes place. The once passive water emerges as a proficient conductor of electricity, primed to facilitate the process of electrolysis. This stands in stark contrast to pure water, which is inherently a poor conductor of electricity.

Electrolysis Amplified

The addition of acid or alkali acts as a catalyst for electrolysis, enhancing the water's ability to shuttle electric charges. This transformation is pivotal in allowing the intended chemical reactions to take place effectively, steering the course of scientific and industrial processes.

As we tinker with the alchemical ballet of water and its transformative dance partners, acid and alkali, we unlock the potential for efficient electrolysis and harness the power of chemistry to shape our world.

Q70:

Hydrogen peroxide should be cooled before use. Why?

A70:

Hydrogen peroxide breaks down into gaseous oxygen when left alone.

3H₂O₂ –> 2H₂O + O₂

When the oxygen was released, it could cause a lot of pressure, and when the bottle was opened, the solution could come out with a lot of pressure. As something cools, the pressure goes down.

Q71:   

Ozone is more water-soluble than oxygen by a factor of 1.5. Why?

A71:

Ozone has a polar composition, whereas oxygen does not. Hence, the solubility of ozone in water, which is also a polar solvent, is greater than the solubility of oxygen in water.

Q72:

AlCl₃ is acidic in aqueous solution. Why?

A72:

In water, AlCl₃ breaks down into Al(OH)₃, a weak base, and HCl, a strong acid. So, the amount of H+ in a solution goes up. So, solution turned out to be acidic.

Q73:

Sodium acetate in water is an alkaline solution. Why?

A73:

In water, sodium acetate breaks down into weak acetic acid and sodium hydroxide (strong). So, the amount of OH- is higher than the amount of H+. So, the solution turned out to be alkaline.

Q74:   

NaCl is protected by a layer of kerosene. Why?

A74:

Sodium reacts easily with atmospheric oxygen and moisture because it is so reactive. Kerosene is used as a barrier to prevent this.

Q75:   

Metals are excellent thermal and electrical conductors. Why?

A75:

The existence of mobile valence electrons, which are able to transfer electricity and heat from one end to the other, is responsible for the material's high electrical and thermal conductivity.

Q76:    

"Defining the Ionic Bond: Electrovalent Harmony": When asked to define "ionic bond" or "Electrovalent bond", how would you?

A76:

The term "ionic bond," often interchangeably referred to as an "electrovalent bond," captures a pivotal aspect of chemical interactions. This unique bond emerges from the captivating interplay of ions from distinct elements, united by the pull of electrostatic forces. Here's a concise breakdown:

Bridging Diverse Ions

Ionic bonds form through the magnetic allure of ions hailing from diverse elements. Typically, these bonds come into existence when a metallic atom partners with a non-metallic counterpart. The resulting connection is an intricate dance of charges – positive and negative – that bind these contrasting ions together.

Power Play of Electronegativity

When metals and non-metals collide, the tussle for electrons ensues. Non-metals, characterized by their stronger pull on electrons, readily wrest these particles from their metal counterparts. This power dynamic shapes the creation of ionic bonds, as electrons traverse from the positively charged metal ions to the negatively charged non-metal ions.

The Unity of Charge

At the heart of an ionic bond lies the essence of electrical balance. The give-and-take of electrons results in one atom turning positively charged while the other takes on a negative charge. When these opposite charges align, the stage is set for the establishment of an ionic bond.

Illuminating Examples

Ionic bonds manifest in compounds like sodium chloride (NaCl) and sulfuric acid (H₂SO₄), showcasing their prevalence in everyday chemistry. Notably, substances linked by ionic bonds often exhibit high melting and boiling points, a testament to the resilience of these connections.

In a universe where atoms harmonize through a symphony of charges, the ionic bond emerges as a foundational force, shaping substances and influencing the properties that define our material world.

Q77:

FeCl₃ with water forms an acidic solution. Why?

A77:

A solution of FeCl₃ in water is acidic because, when dissolved in water, FeCl₃ breaks down into Fe(OH)₃, a weak base, and HCl, a strong acid. So, a solution of FeCl₃ in water is acidic.

FeCl₃ <=> Fe⁺³ + 3Cl^-

3H₂O <=> 3H⁺ + 3OH^-

Fe⁺³ + 3OH^- –> Fe(OH)₃

3H⁺ + 3Cl^- –> 3HCl   

Q78:

Na₂CO₃ in water is an alkaline solution.  Why?

A78:

A solution of Na₂CO₃ in water is alkaline because, when it dissolves in water, it breaks down into NaOH, which is a strong acid, and H₂CO₃, which is a weak acid.

Na₂CO₃ <=> 2Na^- + CO₃^--

2H₂O <=> 2H⁺ + 2OH^-

2Na⁺ + 2OH^- –> 2NaOH

2H⁺ + CO₃^-- –> H₂CO₃

So, a mixture of Na₂CO₃ and water is alkaline because it has more OH^- ions than H⁺ ions.

Q79:   

As an acid, HClO₄ is more powerful than H₃PO₄. Why?

A79:

Because the chlorine in HClO₄ has a higher electronegativity than the phosphorus in H₃PO₄, it is an acid with a higher concentration.

Q80:

Sodium chloride dissolved in water is a neutral solution. Why?

A80:

NaCl in water is neutral because it breaks down into NaOH, which is a strong base, and HCl, which is a strong acid, when it is in water. So, a solution of NaCl in water is neutral.

NaCl <=> Na⁺ + Cl^-

H₂O <=> H⁺ + OH^-

Na⁺ + OH^- –> NaOH

H⁺ + Cl^- –> HCl

Q81:

When potassium metal is placed into water, it immediately ignites. Why?

A81:

Potassium metal reacts with water to produce KOH and hydrogen gas, both of which are flammable.

Q82:

In the process of making of Na, calcium chloride is added to NaCl. Why?

A82:

During electrolysis, calcium chloride is added to NaCl to lower the melting point of NaCl from 815⁰C to 640⁰C, so that the working temperature of the cell is also dropped to 640⁰C. At this temperature, sodium is released smoothly and does not react with the iron container. At 640⁰C, molten electrolytes (NaCl + CaCl₂) don't dissolve molten sodium metal, but at 850⁰C, molten electrolytes dissolve enough molten sodium to make it hard to collect.

Q83:

When compared to Na, K has a lower density. Why?

A83:

Usually, as the number of atoms in a group goes up, so does the density, but K is an exception to this norm. This is because K's atomic volume is almost twice that of Na, yet its atomic weight is not twice that of Na. So, K has a lower density than Na.

Q84:

When it rains, common salt absorbs moisture from the air. Why?

A84:

NaCl is not hygroscopic, but common salt has an impurity called anhydrous magnesium chloride, which is hygroscopic and collects moisture from the air. This is why common salt gets wet when it rains.

Q85:    

"Exploring Group Harmony: Sodium and Copper": In the periodic table, sodium and copper are in the same group. Why?

A85:

The intriguing placement of sodium (Na) and copper (Cu) within the periodic table's arrangement finds its foundation in their electronic configurations. Delve into their atomic symphonies to uncover the essence of their shared grouping:

Unveiling Electronic Arrangements

Sodium, with its atomic number of 11, unveils an electronic configuration of 1s²; 2s² 2p⁶; 3s¹. Copper, on the other hand, boasting an atomic number of 29, showcases a more complex arrangement: 1s²; 2s² 2p⁶; 3s² 3p⁶ 3d¹⁰; 4s¹.

Embracing the Dance of Electrons

The pivotal aspect that binds sodium and copper together lies in the 4s orbital. For copper, this d-orbital is complete with 10 electrons, rendering it a consistent bearer of an oxidation number of 1. This distinctive feature aligns with sodium's single valence electron in its 3s orbital.

United in Group 1

This electrifying symmetry propels sodium and copper into the same group – Group 1. Here, their shared attributes and atomic resonances find a harmonious home, emphasizing the unique traits that emerge when elements gather in similar electronic configurations.

As we journey through the periodic table's intricacies, we encounter the captivating tale of sodium and copper – a testament to the beauty of shared electronic landscapes and the unifying forces that bind elements within the same group.

Q86:

In contrast to copper, whose oxidation state can change, sodium's is always the same. Why?

A86:

Sodium's electronic configuration is 1s²; 2s² 2p⁶; 3s²; and it only has one oxidation state, +1.

In case of Cu, the electronic configuration 1s²; 2s² 2p⁶, 3s² 3p⁶, 3d¹⁰, 4s¹, hence Cu is expected to exhibit only +1 state. Due to the presence of d-orbital electrons, it also exhibit in +2 oxidation state.

Q87:

In contrast to the colourless cuprous salt, cupric salt has a distinct red hue. Why?

A87:

Cuprous ion has an electronic structure of 3d¹⁰, while cupric ion has a structure of 3d⁹. So, the d-d transition is feasible in cupric ion, which is why cupric salts are coloured.

Q88:

The term "alkali metal" refers to sodium. Why?

A88:

The name "alkali metal" comes from the fact that sodium oxide forms a highly alkaline solution when dissolved in water.

Q89:

Copper sulphate solution is an excellent electrical conductor. Why?

A89:

Copper sulphate breaks apart into Cu⁺⁺ and SO₄^-- ions when it is dissolved in water. So, it does a fantastic job of letting energy flow through it.

Q90:

Hydrogen cannot be released from copper by dissolving it in weak sulphuric acid. Why?

A90:

The reducing power of copper is lower than that of hydrogen; hence it cannot convert H⁺ to H₂ gas. As a result, copper does not break down in dilute H₂SO₄ to release H₂ gas.

Q91:

Compared to copper, sodium has a lower melting point. Why?

A91:

Sodium's metallic bond is weaker than copper's. As a result, sodium has a lower melting point than copper.

Q92:

Covering more reactive metals with copper is common practice. Why?

A92:

Copper is used to protect more reactive metals from the elements by applying small layers of basic carbonate on them.

Q93:

Sulphurous vapours arise from a Na₂S-water solution. Why?

A93:

The sulphuric acid smell is due to the reaction between the S^-- in Na₂S and the H⁺ in water.

Q94:

Elements in group IA have a lot of reducing power. Why?

A94:

Elements of group IA easily release electrons because of their low ionization potential. The result became a strong reducing agent.

Q95:

Heating carnallite in the presence of HCl gas produces an anhydrous form of carnallite. Why?

A95:

Heating carnallite in the presence of HCl gas makes anhydrous carnallite, because heating carnallite makes MgO. It is heated in the presence of HCl gas to stop this from happening.

When heated in presence of HCL:

KCl.MgCl₂.6H2O –> KCl.MgCl₂ + 6H₂O

Q96:

What exactly is radioactivity?

A96:

Radioactivity is a process in which the atoms of an element break apart on their own into smaller pieces called Bacquerel rays, which are unseen waves made up of alpha (, beta (, and gamma ( rays. It can also be said that radioactivity is when an atomic nucleus breaks apart on its own to make a steady nucleus that keeps giving off radiations.

Q97:

I'm confused; please explain what "nuclear fission" means.

A97:

Nuclear fission is the process of breaking up atomic nuclei into smaller nuclei by hitting it with high-energy particles, which releases a lot of energy. When chain reactions are managed in reactors, nuclear fission can help people get the energy they need. About 85% of the energy we use now comes from nuclear power.

However, if this process is allowed to continue unregulated, it can eventually give rise to a force that is both powerful and destructive. The appearance of a fungus-like cloud after the blast of a so-called "atomic bomb" is a horrible reminder of the destructive power of fission as well as the strength of the atom itself.

Q98:   

Ammonia solution will dissolve AgCl but not AgI. Why?

A98:

While AgCl can produce a complex compound with NH₄OH, which is soluble, AgI does not have the ability to generate a complex compound.

AgCl + 2NH₄OH <=> [Ag(NH₂)₂]Cl + 2H₂O

AgI + NH₄OH –> NO REACTION

Q99:

The nuclear reactor uses liquid sodium. Why?

A99:

Since liquid sodium is a good heat conductor, it is used in nuclear reactors in the capacity of a coolant.

Q100:

The use of potassium super oxide is common at a high altitude. Why?

A100:

Because potassium super oxide is such a good source of oxygen, it is often utilised as an oxygen source in environments that are particularly high in altitude.

Q101:

The process for making sodium bicarbonate and potassium bicarbonate is different. Why?

A101:

The following reactions are needed for the production of sodium bicarbonate:

NH₂ + H₂O –> NH₄OH

CO₂ + H₂O –> H₂CO₃

H₂CO₃ + NH₄OH –> (NH₄)HCO₃ + H₂O

NaCl + NH₄HCO₃ –> NaHCO₃ + NH₄Cl

NaHCO₃ dissolves less easily than NH₄Cl, while KHCO₃ dissolves more easily than NH₄Cl. So it's hard to separate KHCO₃ from other substances. So, the same method cannot be used to make KHCO₃.

Q102:

Aqua regia dissolves gold, while HCl and HNO₃ do not. Why?

A102:

Aqua regia includes nascent chlorine. Gold will create a complex with the help of the nascent chlorine, and this complex will be soluble. Therefore, gold can be dissolved in aqua regia.

Au + HNO₃ + 4HCl –> HAuCl₄ (Soluble) + NO + H₂O

Q103:

For what reason does Cu(OH)₂ dissolve in KCN?

A103:

With KCN, Cu(OH)₂ forms a complex which is soluble.

Cu(OH)₂ + 4KCN –> K₂[Cu(CN)₄] + 2KOH

Q104:

Hydrogen gas (H₂) is produced during the electrolysis of fused calcium hydride at the anode. Why?

A104:

The hydrogen in calcium hydride (CaH₂) is a negative ion (H^-). During electrolysis, it gets oxidised at the anode and hydrogen gas is released.

During electrolysis: CaH² –> Ca⁺² + 2H^-

At anode: 2H^- –> H₂ + 2e

Q105:  

"Understanding Isobars: A Clear Explanation": To clarify, what exactly are isobars?

A105:

Isobars refer to atoms or nuclei sharing an identical number of nucleons, which is the collective sum of protons and neutrons. This equivalence in nucleon count results in identical atomic masses. Coined by Alfred Walter Stewart in 1918, this term aptly captures the concept. Examples of isobars include Argon-40, Potassium-40, and Calcium-40 – all possessing an atomic mass of 40. However, their proton and neutron counts vary. Another instance arises with Carbon-14, Nitrogen-14, and Oxygen-14, exhibiting the same atomic mass of 14.

In the intricate realm of atomic composition, isobars stand as a fascinating phenomenon, illuminating the intricacies of nucleon interplay and atomic identity.

Q106:

Hydrogen gas (H₂) is produced during the electrolysis of fused NaH at the anode. Why?

A106:

When fused NaH is electrolyzed, hydrogen is split as a hydride (H^-) ion, which releases H₂ gas at the anode.

Electrolysis: NaH –> Na⁺ + H^-

At anode: 2H^- –> H₂ + 2e

At cathode: 2Na⁺ + e –> Na

Q107:

A brown bottle is used to store the silver nitrate solution. Why?

A107:

Due of its sensitivity to light, silver nitrate solution must be stored in a dark brown bottle. When exposed to light, it breaks down into the dark-colored substance Ag.

Q108:

Silver dissolves in diluted HNO₃ but not in HCl. Why?

A108:

Silver generates a soluble silver nitrate when exposed to HNO₃. However, it shows no reactivity when exposed to HCl.

Ag + 2HNO₃ –> AgNO₃ + H₂O + NO₂

Q109:

Solution NH₄OH dissolves silver chloride, however solution HNO₃ does not. Why?

A109:

Because a soluble compound is formed, silver chloride can be dissolved in NH₄OH solution.

AgCl + 2NH₄OH –> [Ag(NH₃)₂]Cl + 2H₂O

AgCl, on the other hand, doesn't make any complex with HNO₃. So, it doesn't mix with HNO₃, but it does with NH₄OH.

Q110:

When MgO is reduced, an inert environment is employed. Why?

A110:

Mg is kept from turning into MgO by using an inert environment. The Mg is then condensed into ingots.

Q111:

Hydrogen is not released from copper when HCl is diluted. Why?

A111:

Copper has a lower electropositive charge than hydrogen, so it can't replace hydrogen ions in acids. Because of this, dilute hydrochloric acid does not affect copper.

Q112:

Nitric acid is capable of dissolving copper. Why?

A112:

Nitric acid is a strong oxidizer that turns Cu into Cu⁺², so copper dissolves in it.

Cu –> Cu⁺² + 2e

2NO₃^- + 4H⁺ + 2e –> 8H₂O + 2NO₂

Q113:

The formula MgCl₂.6H₂O cannot be used to make anhydrous magnesium chloride. Why?

A113:

We can't make anhydrous magnesium chloride by heating MgCl₂.6H₃O, because when we heat it, it breaks down into MgO, H₂O, and HCl.

MgCl₂.6H₂O –> MgO + 2HCl + 5H₂O

Q114:

When carbon dioxide passes through lime water, the water turns milky and then clears. Why?

A114:

There are two phases to the reaction of CO₂ and lime water. It begins by forming a CaCO₃ precipitate, which is visible as a white powder when combined with lime water.

Ca(OH)₂ + CO₂ –> CaCO₃ + H₂O

Ca(OH)₂ becomes calcium bicarbonate, which is soluble in water, when an excess of CO₂ is passed.

Ca(OH)₂ + CO₂ + H₂O –> Ca(HCO₃)₂

This is why lime water turns milky before finally becoming clear.

Q115:

Magnesium undergoes a chemical change when it burns in air. Why?

A115:

Because when Mg burns, it gives off a bright light and turns into a white solid. The solid is made of different materials and has different qualities than the Mg wire. It is not easy to change back to the original state.

Q116:

When asked, "What is a reducing agent?"

A116:

In a chemical reaction, a substance is said to be a reducing agent if its constituent atoms are able to donate or give up electrons. It is said that a reducing agent has become oxidised when it has given up an electron or many electrons. The oxidant is the name given to the atom in a chemical compound that receives an electron or electrons from a reducing substance. The oxidant is made to get reduced as a result of the reducing agent. Reducing agents and oxidising agents are responsible for the process of corrosion. The reducing agent corrodes as a result of its oxidation, which is a natural process. The anode undergoes oxidation while the cathode undergoes reduction during a corrosive process. To put it another way, the oxidising agent accumulates electrodes while the reducing agent corrodes and loses electrons.

Reducing agents come in a wide variety of forms. If an element has a large atomic radius and a low number of electrons in its outermost shell, it is more likely to act as a reducing agent. Zinc, lithium, iron, and oxalic acid are all examples of reducing agents. Some materials can be protected from oxidation with the help of reducing substances if you know what you're doing. As an example, consider galvanised steel. Corrosion is mitigated to some extent by the steel's zinc coating, which remains effective even if damaged. This is due to the higher electron-donating potential of the zinc surrounding the steel compared to the iron within the steel itself during chemical reactions. The steel is preserved from rust because the zinc acts as a reducing agent.

Q117:

When exposed to skin or fabric, AgNO₃ solution produces a dark stain. Why?

A117:

Because silver nitrate is reduced to black metallic silver, it produces a black stain when it comes into contact with skin or fabric.

Q118:  

"Unveiling van der Waals Forces: A Comprehensive Explanation": What is van der Waals force?

A118:

The van der Waals force is named in honour of the Dutch scientist Johannes Diderik van der Waals (1837-1923). It stands as the earliest form of intermolecular force between atoms and molecules. Unlike ionic or covalent bonds, these attractive forces do not arise from a chemical bond. Rather, they are relatively feeble and easily perturbed. The van der Waals forces fade swiftly as the distance between interacting molecules increases. These forces wield immense significance across various scientific realms, including structural biology, nanotechnology, polymer science, and surface science.

Understanding Van der Waals Forces

At its core, van der Waals forces denote short-range interactions between atoms, molecules, and surfaces. These forces can either repel or draw these entities together. In the absence of other forces, the van der Waals contact distance arises when the forces shift from attraction to repulsion as atoms draw nearer. This transition occurs due to the atoms exerting pressure on each other.

Van der Waals forces encompass three distinct types:

• Dispersion (Weak): The least potent of the trio.
• Dipole-Dipole (Medium): Exhibiting a moderate strength.
• Hydrogen (Strong): Standing as the strongest among them.

To derive accurate values for non-ideal gases, the van der Waals equation proves indispensable. The equation, (P + n²a/V²)(V - nb) = nRT, employs several parameters:

• V: Represents the gas volume in moles (n).
• a: Signifies the gas-specific constant.
• P: Indicates the measured pressure (typically low in most scenarios).
• b: Reflects the eliminated volume per mole.
• R: Corresponds to a known constant with a value of 0.08206 L atm mol⁻¹ K⁻¹.
• T: Denotes the temperature.

Van der Waals forces, an intricate web of interactions, shape the behavior of substances and lay the foundation for myriad scientific explorations.

Q119:

Limestone is added to iron rock in the process of making iron. Why?

A119:

At 1000°C, lime stone breaks down into CaO and CO₂. During the extraction process, CaO mixes with the gangue (SiO₂) in the red haematite ore to make CaSiO₃ slag, which is then thrown away.

CaCO₃ –> CaO + CO₂

CaO + SiO₂ –> CaSiO₃

Q120:

Instead of using fused calcium chloride, quick lime is utilised to dry ammonia. Why?

A120:

Quick lime did not make an association with NH₃, but anhydrous calcium chloride did. So, calcium chloride without water is not used to dry NH₃.

Q121:

You can't dehydrate alcohol using anhydrous CaCl₂.  Why?

A121:

CaCl₂ and alcohol combine to make the compound CaCl₂, 4C₂H₂OH. So, you can't use CaCl₂ without water to dry alcohol.

Q122:  

"Unravelling Covalent Bonds: An In-Depth Explanation": What is covalent bonding defined as?

A122:

Covalent bonds represent a specific form of chemical bonding that takes place exclusively among non-metallic atoms. These bonds stand distinct from other bonding types due to their unique characteristic – the sharing of electron pairs.

The Formation of Covalent Bonds

When two non-metallic elements with closely matched electro-negativities unite, covalent bonds emerge. In this connection, electrons are not exchanged between the atoms, as neither possesses the requisite "strength" to do so. Instead, they engage in a reciprocal sharing of electrons from their respective outer molecular orbits, contributing to the stabilization of other molecules.

Understanding Covalent Connections

Covalent bonds manifest when two non-metallic atoms establish a connection. In this intricate dance, atoms partake in the sharing of electrons, weaving a bond that facilitates their structural harmony. These bonds come with relatively low melting and boiling points, setting them apart from other bonding types.

Illustrative Examples

Hydrochloric acid (HCl) and methane (CH₄) offer vivid illustrations of covalent bonding in action. These compounds exemplify the captivating interplay between atoms as they share electrons, fostering molecular stability within the realm of covalent chemistry.

Q123:

In the electrolytic production of Ca, CaF₂ is combined with anhydrous CaCl₂. Why?

A123:

When CaF₂ is added to pure CaCl₂ the melting point drops from 773⁰C to 600⁰C. This means that the working temperature of the electrolytic cell stays between 700 and 750C. CaF₂ also makes it easy for the released Ca molecules to stick together, which is what happens at the cathode. It lowers the voltage at which CaCl₂ breaks down even more.

Q124:

Half-life period: what does that mean?

A124:

The half-life is the duration of time it takes for a substance to diminish to half of its initial amount.

T(1/2) = 0.693/λ        

Where  = radio active decay constant.

Q125:

What exactly do you mean when you talk about isotones?

A125:

Isotones refer to atoms that contain the same number of neutrons but different number of protons. They are atoms of a distinct element with the same number of neutrons but different mass and atomic numbers. If the neutron count of two nuclides is the same but the proton count is different, we call them isotones.

For instance, both Boron-12 and Carbon-13 nuclei contain 7 neutrons. The atomic number is different from the mass number.

Most elements with an odd number of neutrons are isotonic, establishing that odd neutron configurations are relatively more stable than even neutron configurations.

The number of neutrons in calcium and potassium, for instance, is 20. That's why we call them isotones. Silicon and phosphorus, for instance, both have neutron number 16, but their respective masses are 30 and 31, and their atomic numbers are 14 and 15.

Q126:

So, tell me additionally, what exactly is an oxidising agent?

A126:

In a redox reaction, an oxidising agent is a reactant that transfers electrons to another reactant.

Typically, the oxidising agent will absorb these electrons, becoming reduced as a result.

To put it another way, an oxidising agent is an electron acceptor.

An oxidising agent is any species that can provide electronegativity (in this case, oxygen) to another.

Some other names for oxidising agents include oxidants and oxidizers.

Nitric acid, potassium nitrate, ozone, and hydrogen peroxide are all examples of oxidising agents. Chlorine, bromine, and fluorine are just a few examples of halogens that act as oxidizers.

When a chemical reaction takes place, one of two things happens: either the oxidising agent or the reducing agent obtains electrons and is reduced, or the reducing agent loses electrons and is oxidised.

Depending on the circumstances, an oxidizer could be considered hazardous because of its potential to promote combustion. The danger sign for an oxidizer is a red circle with flames emerging from the top.

Q127: 

In contrast to the other halogens, fluorine does not show higher oxidation states or variable valency. Why?

A127:

As fluorine belongs to the second period of the periodic table, its second energy shell does not include any d orbitals. As a result, it does not exhibit a higher oxidation state, in contrast to other halogens, which have available d-orbitals that are vacant. As a result of this, they have a higher oxidation state or variable valency.

Q128:

The atoms that make up inert gases do not have the capability of combining together to create polyatomic molecules. Why?

A128:

The electronic structure of an inert gas is stable. All of their shells, even the one on the outside, are full. So, they can't make molecules with more than one atom.

Q129:  

"Decoding Coordinate Covalent Bonds: A Comprehensive Insight": What exactly are coordinate covalent bonds?

A129:

Coordinate covalent bonds, also known as dative covalent bonds, represent a distinctive subset within the realm of covalent bonding. These bonds materialize when two non-metal atoms partake in the sharing of a pair of electrons to form a covalent bond. However, what sets coordinate covalent bonds apart is the unequal contribution of electrons: only one of the participating atoms donates the electron pair responsible for bonding.

The Dance of Donor and Acceptor:

In this intricate dance, the atom bestowing the lone pair of electrons assumes the role of the donor, elegantly referred to as the Lewis base. On the opposite end, the atom accepting the gifted electron pair into an unoccupied orbital earns the title of the Lewis acid – a recipient poised to complete the bonding picture.

Essential Concepts Illuminated:

• Covalent Bond Foundation: Covalent bonds emerge when two non-metal atoms mutually share a pair of electrons.
• Distinctive Feature of Coordinate Covalent Bonds: These bonds emerge from the unilateral contribution of an electron pair by one participating atom.
• The Lewis Base: The entity relinquishing the lone pair of electrons embraces the role of the Lewis base, embodying the essence of donation.
• The Acceptor Atom: Positioned as the Lewis acid, this atom welcomes the incoming electron pair into an available orbital.

Intriguing Instances Explored:

• Hydronium Ions (H₃O⁺): These formations occur when water molecules intricately establish covalent bonds with hydrogen ion atoms (H⁺) within environments of acidity.
• Covalent Bonds in Action: The rich interplay of covalent bonds extends to the establishment of connections between diverse metal ions and up to six water molecules.
• Triatomic Beryllium Chloride (BeCl₂) Chains: The molecules of triatomic beryllium chloride ingeniously intertwine through covalent bonds, paving the way for the creation of elongated chains.

The intricate world of coordinate covalent bonds opens a portal to the captivating mechanisms of electron sharing, atom synergy, and molecular harmony.

Q130:  

"Demystifying Oxidation: A Closer Look": So, tell me, what exactly is oxidation?

A130:

Oxidation unfolds as a pivotal phenomenon in the realm of chemical reactions. It occurs when a molecule, atom, or ion relinquishes an electron, bringing about a transformative change. This process, commonly referred to as oxidation, is characterized by an elevation in the oxidation state of the entity undergoing the change. As a counterpart to oxidation, the process of reduction unfolds – a state where electrons are gained or the oxidation status of an atom, molecule, or ion is diminished.

Illuminating Instances:

One illustrative instance of oxidation occurs in the formation of hydrofluoric acid from the interaction of hydrogen and fluorine gas:

H₂ + F₂ → 2HF

In this reaction, a noteworthy transformation takes place. Hydrogen undergoes a reduction process, while fluorine, its counterpart, experiences oxidation. Viewing this reaction as a summation of two halves can offer clearer insights:

Half-Reaction 1:

H₂ → 2H⁺ + 2e⁻

Half-Reaction 2:

F₂ + 2e⁻ → 2F⁻

Noteworthy Observation:

It's important to highlight that oxygen remains uninvolved throughout the entirety of this reaction. This spotlight on the intricate dance of electrons – where some are relinquished while others are gained – unveils the captivating world of oxidation and its closely intertwined partner, reduction.

Q131:

What does the concept of reduction mean?

A131:

In a reduction, an electron is gained by a chemical species, lowering its oxidation number. The oxidation part of the reaction is where electrons are lost. Redox reactions (reduction + oxidation = redox) are the combination of these two processes. The process of reduction can be seen as the opposite of oxidation.

There are reactions where oxygen is transferred between the two states (oxidation and reduction). Oxidation in this context means oxygen is being added, while reduction means oxygen is being taken away.

One definition of oxidation and reduction, although out-dated and hardly used now, views the process through the lens of protons or hydrogen. In this context, oxidation refers to the loss of hydrogen and reduction refers to its gain.

Electrons and oxidation numbers are key components of the most exact description of reduction.

For example, in the process, the H⁺ ions, which have an oxidation number of +1, are turned into H₂, which has an oxidation number of 0.

Zn(s) + 2H⁺(aq) –> Zn²⁺(aq) + H₂(g)

Q132:  

"Deciphering Oxidation Numbers: A Comprehensive Exploration": When you say "oxidation number," what do you mean?

A132:

Delving into the intricacies of chemical processes often unveils the significance of oxidation numbers – a fundamental concept that plays a pivotal role in understanding transformations and even naming chemical products. An oxidation number of an atom is a depiction of the hypothetical charge that atom would possess if it existed as ions.

Key Insights Illuminated:

• Basis of Neutrality: In the realm of neutral materials comprised of a single type of atom, each atom stands endowed with an oxidation number of 0. This principle finds its application in various entities, such as O₂, O₃, P₄, S₈, and even the robustness of aluminium metal.
• Hydrogen's Dynamic Role: Hydrogen's alliance with non-metals, as observed in CH₄, NH₃, H₂O, and HCl, propels its oxidation number to ascend by one.
• Synchronization of Ion Charge: The oxidation number of a simple ion harmoniously aligns with its charge. For instance, the Na⁺ ion boasts an oxidation number of 1, while the Cl^- ion assumes a charge of -1.
• Group IA Metal Bonds: The amalgamation of metal atoms brought about by Group IA metals, evident in compounds like Li₃N and Na₂S, results in a uniform oxidation number of +1.
• Group IIA Metal Partnerships: Group IIA elements orchestrate combinations such as Mg₃N₂ and CaCO₃, where the oxidation number of the involved metal atoms uniformly stands at +2.
• Group VIIA Element Alliances: Collaborations involving Group VIIA elements, as seen in AlF₃, HCl, and ZnBr₂, showcase the non-metal assuming an oxidation number of -1.
• Hydrogen's Metal Affiliation: When hydrogen aligns with a metal in compounds like LiH, NaH, CaH₂, and LiAlH₄, its oxidation number transitions to -1.
• Neutrality at Play: In neutral substances, the cumulative sum of oxidation numbers harmoniously equals 0. For example, in the iconic H₂O molecule, the equation unfolds as 2(+1) + (-2) = 0.
• Periodic Table Dynamics: Elements nestled in the lower left corner of the periodic table tend to gravitate towards positive oxidation numbers, while those situated in the upper right corner exhibit an inclination towards negative oxidation numbers. An illustration of this occurs in SO₂, where sulphur garners a positive oxidation number due to its positioning below oxygen on the periodic table: (+4) + 2(-2) = 0.

The labyrinth of oxidation numbers invites us to explore the charged interactions and dynamic configurations that illuminate the language of chemical transformation.

Q133: 

"Determining Oxidation Numbers in Compounds: Unveiling Chemical Signatures": Find the oxidation number of each element in the following compounds:

(i) BaO₂    

(ii) (NH₄)₂MoO₄     

(iii) Na₃Co(NO₂)₆      

(iv) CS₂

A133:

(a) In the compound BaO₂, envisioning oxygen with an oxidation number of -2 would necessitate barium adopting an improbable +4 oxidation state. However, Group IIA elements like barium can't attain a +4 oxidation state. Therefore, this compound is barium peroxide, [Ba²⁺][O₂^2-], where barium carries a +2 oxidation number and oxygen embraces a -1 oxidation state.

(b) Within (NH₄)₂MoO₄, the NH⁴⁺ ion comes to the fore, featuring hydrogen at +1 and nitrogen at -3. Since two NH⁴⁺ ions are present, the counterpart of the compound comprises an MoO₄^2- ion. Here, molybdenum shoulders a -6 oxidation number while oxygen adopts -2.

(c) Sodium invariably resides in the +1 oxidation state across its compounds. Consequently, the compound encompasses the Co(NO₂)₆^3- complex ion. This intricate formation consists of six NO^2- ions, with nitrogen adorned in a +3 oxidation number and oxygen draped in -2. Consequently, the cobalt atom assumes an oxidation state of +3.

(d) The element with the highest electronegativity consistently carries a negative oxidation number. For CS₂, sulphur’s proclivity for forming -2 ions renders its oxidation number as -2, while carbon's stands at +4.

Navigating the intricate terrain of oxidation numbers bestows upon us the power to decipher the chemical narratives woven within compounds, unveiling the dynamic dance of electron-sharing and electronegativity.

Q134:

Put each of the following reactions into one of two categories: metathesis or oxidation-reduction. Take note that there are three common oxidation states for mercury: mercury metal, Hg₂²⁺ ions, and Hg²⁺ ions.

(i) Hg₂²⁺(aq) + 2OH^-(aq) –> Hg₂O(s) + H₂O(l)

(ii) Hg₂²⁺(aq)  + Sn²⁺(aq) –> 2Hg(l) + Sn⁴⁺(aq)

(iii) Hg₂²⁺(aq) + H₂S(aq) –> Hg(l) + HgS(s) + 2H⁺(aq)

(iv) Hg₂CrO₄(s) + 2OH^-(aq) –> Hg₂O(s) + CrO₄^2-(aq) + H₂O(l)

A134:

(i) Metathesis.  Mercury is in the +1 oxidation state in both the Hg₂²⁺ ion and in [Hg₂²⁺][O^2-].

(ii) Oxidation-reduction.  Mercury is reduced from the +1 to the 0 oxidation state, while tin is oxidized from +2 to +4.

(iii) Oxidation-reduction.  This is a disproportionation reaction in which mercury is simultaneously reduced from +1 to 0 and oxidized from +1 to +2.

(iv) Metathesis.  Mercury is in the +1 oxidation state in both [Hg₂²⁺][CrO₄^2-] and [Hg₂²⁺][O^2-].

Q135:  

"Probing Deeper into Acids and Bases: The Brnsted-Lowry Theory": When you say the Lowry and Bronsted theory of acids and bases, what exactly do you mean?

A135:

The Brnsted-Lowry acid-base theory, coined after the collaborative efforts of Johannes Nicolaus Brnsted and Thomas Martin Lowry, introduces a comprehensive framework for categorizing species as strong or weak acids and bases based on their propensity to either donate or accept protons (H⁺). This theory spotlights the pivotal role of proton transfer in acid-base interactions, leading to the formation of conjugate acids and bases. Brnsted and Lowry independently developed this theory in 1923.

Distinctive Aspects of the Brnsted-Lowry Theory:

(1) Proton Handover: At the core of the Brnsted-Lowry acid-base theory lies the concept of proton transfer. An acid relinquishes a proton to a base, resulting in the emergence of a conjugate base from the original acid and a conjugate acid from the initial base.

(2) Widened Applicability: In contrast to the limited scope of the Arrhenius theory, which is confined to aqueous environments, the Brnsted-Lowry theory is more expansive in its application, accommodating a broader range of chemical scenarios.

(3) Fundamental Concepts: Central tenets of the Brnsted-Lowry theory encompass:

• A Brnsted-Lowry acid denotes a substance capable of bestowing a proton (H⁺).
• A Brnsted-Lowry base is an entity with the capacity to accept a proton, characterized by a free electron pair.
• Acidic entities generate their corresponding conjugate base when they donate a proton, while bases engender a conjugate acid upon proton acceptance.
• Strong acids or bases achieve full ionization in solutions, while their weak counterparts exhibit partial dissociation.
• Water exhibits amphiprotic behavior, serving as both an acid and a base in diverse contexts.

(4) Practical Application and Illustrations: Employing the Brnsted-Lowry theory to chemical reactions aids in the identification of acids and bases. For instance, the interaction between ammonia (NH₃) and hydrogen chloride (HCl) leading to solid ammonium chloride (NH₄Cl) highlights HCl as the Brnsted-Lowry acid and NH₃ as the Brnsted-Lowry base. This diverges from Arrhenius acid-base classifications, which are exclusive to aqueous solutions.

(5) Distinguishing Between Strong and Weak Species: A fundamental distinction between strong and weak acids and bases pertains to the extent of ionization. While strong species fully dissociate into ions, weak ones maintain equilibrium between the original and dissociated forms. The direction of the reaction is indicated by arrow directions in the equation.

(6) Equilibrium and Balance: Factors related to equilibrium and pH calculations contribute to determining the course of reactions involving weak acids and bases. Certain substances exhibit dual nature, acting as weak acids or bases depending on the context. An illustrative example is hydrogen phosphate (HPO42-), which showcases amphoteric characteristics, functioning as an acid or a base based on specific circumstances.

(7) Versatility across Solvents: The Brnsted-Lowry theory transcends beyond aqueous solutions. Regardless of the solvent, any reaction involving the transfer of protons between reactants aligns with this theory's principles.

(8) Commanding Acid-Base Knowledge: Proficiency in understanding the Brnsted-Lowry acid-base theory equips chemists with the ability to predict reaction outcomes, discern acids and bases in diverse scenarios, and unravel the intricate choreography of proton dynamics within chemical processes.

The Brnsted-Lowry acid-base theory unveils the subtle intricacies of proton exchange, enriching our comprehension of molecular behaviour and bolstering our capability to comprehend and manipulate chemical reactions across a spectrum of environments and contexts.

Q136:

In this chemistry equation, pick out the Brnsted-Lowry acid and the Brnsted-Lowry base.

C₆H₅OH + NH₂⁻ –> C₆H₅O⁻ + NH₃

A136:

The C₆H₅OH molecule is the proton giver and the Brnsted-Lowry acid. It gives up an H⁺. The Brnsted-Lowry base is the amide ion (NH₂^-), which is taking the H⁺ ion to become NH₃.

Q137:

Find the corresponding pairs of acids and bases in this balance.

(CH₃)₃N + H₂O <=> (CH₃)₃NH⁺ + OH^–

A137:

One pair is H₂O and OH^-, where H₂O has one more H⁺ and is the conjugate acid and OH has one less H⁺ and is the conjugate base.

The other pair is (CH₃)₃N and (CH₃)₃NH⁺.

(CH₃)₃NH⁺ is the conjugate acid (it has an extra proton) and (CH₃)₃N is the conjugate base.

Q138:

When you say "conjugate acids and bases," what do you mean?

A138:

When compared to the original base, the conjugate acid has one more hydrogen atom and one more positive charge.

Conjugate bases are created when an acid loses an H atom and gains a negative charge, making the resulting compound more basic.

As an illustration, consider the formation of carbonic acid and hydronium ions when bicarbonate ions combine with water.

HCO₃^- + H₂O –> H₂CO₃ + OH^-

Base + Acid –> Conjunctions A + Conjunction B

We observe that HCO₃^- is converted to H₂CO₃. One extra H atom and a positive charge (-1 plus 1 equals 0) are present. Therefore, H₂CO₃ is the acid conjugate of HCO₃^-.

Turning H₂O into OH^-. It contains one less hydrogen atoms and one more negative charge. This means that OH^- is the conjugate base of H₂O.

Q139:

HClO₄, H₂S, PH₄⁺, and HCO₃^- are all acids; identify their conjugate bases. For the bases CN^-, SO₄^2-, H₂O, and HCO₃^-, what is the conjugate acid?

A139:

For this analysis, we are given a list of species and asked to identify their conjugate base and conjugate acid, respectively.

A substance's conjugate base is the same thing as its parent but with one proton removed, while its conjugate acid is the same thing as its parent but with one proton added.

ClO₄^- is HClO₄ minus one proton, or H⁺.  HS^–, PH₃, and CO₃^2- are also conjugate bases.

A proton (H⁺) is added to CN^-, creating HCN. We also have HSO₄^-, H₃O⁺, and H₂CO₃ as cases of other conjugate acids.

Hydrogen carbonate ion (HCO₃^-) is amphiprotic, as should be obvious. It has the ability to function as both an acid and a base.

Q140:  

To clarify, could you please explain the Lewis theory of acids and bases?

A140:

Understanding the Lewis Theory of Acids and Bases:

The Lewis theory of acids and bases, formulated by Gilbert N. Lewis, provides a fresh outlook on chemical interactions by emphasizing the role of electron pairs. Diverging from the Brnsted-Lowry theory, which centers on proton transfer, the Lewis theory revolves around the sharing of electron pairs between substances.

Electron Pair Donors and Acceptors:

According to the Lewis theory, a substance qualifies as a Lewis acid if it can accept an electron pair, while a Lewis base is identified by its ability to donate an electron pair. This electron-centric framework widens the scope of understanding acid-base relationships and extends it to a broader array of chemical scenarios.

Extending Beyond Protons:

An inherent strength of the Lewis theory lies in its applicability beyond systems involving hydrogen ions. This adaptability renders it a versatile tool for explaining a diverse array of chemical reactions that transcend aqueous solutions.

Revisiting Hydrogen Ion Interactions:

Consider the interaction between hydrogen ions and hydroxide ions:

H⁺ + OH^- –> H₂O

From a Lewis perspective, the hydroxide ion functions as a Lewis base by sharing an electron pair with the hydrogen ion, which functions as a Lewis acid. This shift in focus, from proton transfer to electron sharing, introduces novel insights into chemical reactivity.

Interlinking with Other Theories:

The Lewis theory establishes connections with other acid-base models:

• Brnsted-Lowry Nexus: Every Brnsted-Lowry acid or base corresponds to a Lewis acid or base, emphasizing the interconnectedness of different theories.
• Enriched Acidic Definition: Lewis acids exhibit behaviors that do not always align with the Brnsted-Lowry or Arrhenius definitions, accommodating the identification of unconventional acidic attributes.

Illuminating Complex Bonding Arrangements:

The Lewis theory proves especially advantageous in comprehending intricate bonding featuring dative coordinates. Its relevance extends to transition metal chemistry and processes where water serves as a solvent, contributing to an enhanced grasp of intricate chemical phenomena.

A Holistic Viewpoint:

By embracing the Lewis theory, chemists gain a comprehensive comprehension of acid-base interactions. The theory's emphasis on electron pairs deepens insights into the fundamental mechanisms governing chemical reactions. As we navigate the complexities of chemistry, the Lewis theory stands as a guiding principle, illuminating new avenues and broadening our horizons.

Q141:

Find the Lewis acid and Lewis base in each reaction.

(a) BH₃ + (CH₃)₂S –> H₃B:S(CH₃)₂

(b) CaO + CO₂ –> CaCO₃

(c) BeCl₂ + 2Cl⁻ –> BeCl₄²⁻

A141:

(a) The valence electron count for boron in BH₃ is just 6. Since it lacks an electron, it can accommodate a lone pair. (CH₃)₂S contains a sulphur atom with two lone pairs, similar to oxygen. As a result, the sulphur atom in (CH₃)₂S gives up an electron pair to the boron atom in BH₃. The Lewis acid is BH₃, and the Lewis base is (CH₃)₂S.

(b) Since oxygen in CaO can donate an electron pair, CaO is the Lewis base. CO₂ is the Lewis acid because carbon accepts two electrons.

(c) There are four lone pairs in the chloride ion. In this process, BeCl₂, which only has four electrons surrounding Be, receives a lone pair from each chloride ion. Since BeCl₂ is an acid, chloride ions are bases.

Q142:

Magnesium oxide (MgO) is typically used to line ovens and furnaces. Why?

A142:

Some ovens have walls made out of magnesium oxide. It is called a "refractory material", which means it can stand up to heat. Magnesium oxide can stand up to the high temperatures in a furnace because it has a high melting point of 2852°C. The strong ionic bonds between the small Mg²⁺ and O^2- ions make its melting point high.

Magnesium oxide is a base oxide, so it can't be used in furnaces where acids might be present. But it doesn't do anything with other simple substances like calcium oxide. Because of this, it can be used in the furnaces that make iron and steel.

Limestone is one of the raw materials that are put into the Blast Furnace. When that breaks down in the heat of the boiler, it turns into basic calcium oxide. This would have no effect on a basic lining for a refractory burner, like magnesium oxide.

In the process of making basic oxygen steel, quicklime (calcium oxide) is added to the furnace to clean the iron of any impurities. Again, this will have no effect on the magnesium oxide coating.

Q143:

Fires created by the burning of Mg-metal cannot be put out using CO₂. Why?

A143:

When magnesium is burned, heat is produced, which in turn breaks down carbon dioxide into carbon and oxygen. The process of burning of magnesium is made easier by the presence of this oxygen. Because of this, carbon dioxide (CO₂) is not utilised in the putting out of fires caused by magnesium.

2Mg + CO₂ –> 2MgO + C

Q144:

It is not the case that a standard solution of NaOH is prepared by dissolving its weight. Why?

A144:

It is not at all impossible to make a standard solution of sodium hydroxide (NaOH). However, this cannot be done by directly weighing NaOH and then dissolving it to a precise volume. This is due to the fact that NaOH is not and cannot be used as a main standard.

It is not commercially available in a level of purity that is sufficient, and more significantly, it is so hygroscopic that accurate weighing of it is impossible unless considerable efforts are taken to eliminate damp air from the environment.

Therefore, in order to construct a standard solution of NaOH, we would first need to generate a nominal concentration, such as 0.1 M, and then standardise it by titrating it against a primary standard. Only then would the solution be considered a NaOH standard solution.

Potassium hydrogen phthalate, sometimes known as KHP, is the form that is most frequently utilised. Even if the results of our titration show that the actual concentration is 0.1053 M or any other concentration that is close to 0.1 M, the solution in question is still considered to be a standard solution.

Q145:

When heated, ZnO turns yellow, but when cooled, it turns white. Why?

A145:

As zinc oxide crystals are heated or flamed with a blowtorch in the presence of air, the colour of the zinc oxide changes from white to yellow as the heat is applied. When the heat is removed, the zinc oxide reverts to its original colour of white.

This is because of a non-stoichiometric defect known as the phenomenon of metal surplus defect, which is caused by the presence of additional ions in intermediate locations.

When ZnO is heated, the oxygen escapes in the form of 2O₂, leaving behind Zn²⁺ and two electrons.

The formula can be found as follows:

ZnO –> Zn²⁺ + (1/2) O₂ + 2e^-

Zn²⁺ and the two electrons move to the spaces between the crystal sites. This gives the ZnO crystal structure more electrons. Also, the crystal has more zinc than it needs, so its formula is Z_n1+xO. The extra Zn²⁺ ions move to intermediate locations, and the extra electrons move to intermediate locations next to them. When light hits these crystals, the electrons take in some of the light in the visible range. This makes the ZnO look yellow.

Q146:

If you want to make hydrogen, you should utilise zinc with either hydrochloric acid or sulfuric acid, but not with nitric acid. Why?

A146:

The addition of nitric acid to most metals does not result in the release of hydrogen gas since nitric acid is such a powerful oxidising agent. Nitric acid reacts with zinc to produce ammonium nitrate at very low concentrations.

4Zn + 10HNO₃ –> 4Zn(NO₃)₂ + NH₄NO₃ + 3H₂O

And therefore, zinc is combined with hydrochloric acid or sulfuric acid to create hydrogen.

Q147:

The common salt purification process involves HCl because of why.

A147:

There are numerous insoluble and soluble contaminants in regular table salt. Prepare a saturated solution of table salt, then filter out any insoluble contaminants. The saturated solution goes through a cycle with hydrogen chloride gas (HCL).

HCL and NaCl separate into their corresponding ions as follows:

HCL <=> H⁺ + Cl^-

NaCl <=> Na⁺ + Cl^-

Due to the ionisation of HCL, the concentration of Cl^- ions in solution significantly increases. As a result, pure sodium chloride comes out of solution because the ionic product [Na⁺][Cl^-] exceeds the sodium chloride's product of solubility.  

Q148:  

Explain why cations have smaller radii than their parent atoms and anions have larger radii.

A148:

Atoms feature a nucleus with positively charged protons and surrounding electron shells with negative charges. This arrangement contributes to the distinct radii exhibited by cations and anions, charged forms derived from parent atoms.

Cations: Reduced Radii

Cations, formed through electron loss, demonstrate smaller radii compared to their parent atoms. This phenomenon arises from shifts in the balance between protons and electrons. With the loss of an electron, the nucleus's positive charge gains prominence, pulling the remaining electrons closer. As a result, the electron cloud contracts, leading to a decrease in ion radius. For instance, the sodium ion (Na⁺) has a radius of 95 pm, notably smaller than the 186 pm radius of a neutral sodium atom (Na).

Anions: Expanded Radii

Conversely, anions, created when atoms gain electrons, exhibit larger radii than their parent atoms. The introduction of additional electrons alters electron-electron repulsion within the electron cloud. Despite a consistent positive nuclear charge, the increased electron repulsion prevails. This weakens the attraction between electrons and the nucleus, causing outermost electron shells to expand. Consequently, anions showcase larger radii. For instance, the fluoride ion (F^-) boasts a radius of 136 pm, while the fluorine atom (F) has a smaller radius of 64 pm.

Balance of Charges and Radii

The variation in radii between cations and anions reflects the delicate balance between the nucleus's positive charge and the electron's negative charge. Cations' reduced radii stem from intensified attraction between the electron cloud and the positively charged nucleus. Conversely, anions' expanded radii result from increased electron-electron repulsion counteracting the nucleus's attraction.

Dynamic Nature of Charge

The radii alteration observed in cations and anions underscores the dynamic and responsive nature of atomic behavior. Electron gain or loss orchestrates size changes, playing a pivotal role in determining the properties and interactions of these charged entities.

Atoms have a positive charge at their nucleus, which is made up of positively charged protons, and a negative charge at each of the electron shells that rotate around the nucleus.

So, here's how it works out for cations and anions:

When one electron is lost during the process of creating a cation, the ensuing anion has a higher effective nuclear charge than the parent atom. Cations are smaller than their parent atoms because of this. The sodium ion has a radius of 95 pm, while the Na atom has a radius of 186 pm.

Anions, on the other hand, are larger than their parent atoms, making them negatively charged. This is because when extra electrons are added to an atom to form an anion, the nuclear charge remains the same but the electrons repel each other more strongly, resulting in a lower effective nuclear charge. The radius of a fluoride ion, for instance, is 136 pm, but that of a fluorine atom is just 64 pm.

Q149:

So, let me get this straight: what exactly is redox titration?

A149:

A titration is a procedure used by chemists to determine the precise quantity of base required to neutralise an acid. A titration can also be used to calculate how much oxidizer must be added to a reducing agent for the reaction to occur. Titrations of this type are known as redox titrations.

Redox reactions include the transfer of electrons between reactants, resulting in a shift in the oxidation states of atoms in both the reactants and the products.

When a substance gains an electron, we call it reduced, and when it loses one, we call it oxidised. The oxidised species donates an electron to the reduced species during the redox process.

A reducing agent is a substance that adds electrons to another substance. When an oxidising agent drops electrons, it is said to be "reduced". On the other hand, the oxidising agent oxidises (takes electrons from) another species, so it gains an electron and becomes reduced.

The oxidation number (or oxidation state) of an atom tells chemists whether or not the atom is positively or negatively charged and how many electrons it has received or lost during a process.

Redox titrations include the titration of an oxidising agent with a reducing agent (or vice versa). Potassium dichromate can be used to titrate a solution of iron(II) chloride, for instance. The Cr₂O₇^2- solution is added to the Fe²⁺ solution during the titration. As it converts the Fe²⁺ to the more stable Fe³⁺, the dichromate ion is reduced to Cr³⁺.

Redox titrations come in a variety of forms, each of which is typically referred to by the reagent it uses: First, there's permanganometry; second, cerimetry; third, iodometry; fourth, dichrometry; fifth, bromometry; and sixth, iodometry.

Q150:

If you titrate iodine, what exactly are you doing?

A150:

Iodine is a weak oxidising agent that undergoes reduction to produce the iodide anion.

I₂(aq) + 2e^- <=> 2I^-(aq)

E^o = 0.621 V

Iodide anion is a fairly weak reducing agent that will react with oxidising analytes to produce iodine since the redox reaction described above is reversible. Many oxidising and reducing substances can be analysed by using iodine titrations.

Iodimetric titrations include the reaction of the analyte (a reducing agent) with iodine to create iodide, as shown by the equation:

A_ox + I₂ –> A_red + 2I^-

Iodometric titrations include the production of iodine from the reaction of the analyte (an oxidising agent) with an unaccounted-for excess of iodide:

A_red + 2I^- –> A_ox + I₂

Q151:

What exactly are the meanings of acid and base indicator?

A151:

Utilising an acid base indicator is the most typical way to obtain a rough estimate of the pH of a solution. A big organic molecule that functions in a manner like to that of a "colour dye" is referred to as an indicator. There are numerous molecules that respond to a change in the concentration of hydrogen ions. These molecules are referred to as acid-base indicators. The majority of dyes do not change colour depending on the quantity of acid or basic that is present. The majority of the indicators are, on their own, weak acids.

"Litmus" paper is the most usual way to tell. Below pH 4.5, it's red, and above pH 8.2, it's blue.

Various other commercial pH papers can display colours for each major pH unit. A mixture of indicators called Universal Indicator is able to provide a full range of colours for the pH scale.

At different pH levels, a number of indicators undergo colour changes. You may visibly ‘indicate’ the approximate pH of a sample by using an acid-base indicator that has been properly chosen. A weak organic acid or basic dye that changes colour at specific pH levels serves as an indication most of the time. The weak acid positive ion (In^-) will have a different colour from the weak acid form (HIn).

The equilibrium of weak acids is:

H⁺ + In^- = HIn

(1) pH 8.2 is colourless for phenolphthalein and pH 10 is red.

(2) pH 3 is yellow for bromophenol blue, while pH 4.6 is blue.

Q152:

Ba(OH)₂ is insoluble in concentrated H₂SO₄, but it dissolves in dilute HCl. Why?

A152:

When combined with H₂SO₄, Ba(OH)₂ forms insoluble barium sulphate.

Ba(OH)₂ + H₂SO₄ –> BaSO₄ + 2H₂O

However, dilute HCl reacts with Ba(OH)2 to form soluble barium chloride.

Ba(OH)₂ + 2HCl –> BaCl₂ + 2H₂O

This explains why Ba(OH)₂ is insoluble in concentrated H₂SO₄ but soluble in HCl.

Q153:

Bleaching powder loses its bleaching property when it is kept open for a long time.

A153:

Chloride of lime, more often known as bleaching powder, has a solid texture and appears yellowish white in colour. The chlorine smell of bleaching powder is unique. As its name suggests, bleaching powder is used to remove colour. It can also be used as bleach.

Here are three important things to know about bleach:

(1) When bleach is mixed with water, it kills germs better than when it is used straight from the bottle.

(2) Bleach goes bad. Bleach starts to go bad after it has been stored for six months. Bleach loses 20% of its power every year, even if it stays in the same bottle.

(3) We shouldn't mix bleach with cleaners that contain ammonia. When you mix bleach and ammonia, you can make poisonous gases called chloramines and an explosion called “nitrogen trichloride”.

Bleaching powder releases chlorine gas when it combines with atmospheric moisture. As a result, the bleaching power of the powder is destroyed. It can be written as:

Ca(OCl)Cl + H₂O –> Ca(OH)₂ + Cl₂

Q154:  

Why Does Heating Affect Magnesium Carbonate but Not Sodium Carbonate?

A154:

Introduction

When heat is applied to certain chemical compounds, interesting reactions can occur. One such case involves magnesium carbonate and sodium carbonate. In this discussion based answer, we'll explore the reasons behind why heating causes magnesium carbonate to break down into carbon dioxide and magnesium oxide, while sodium carbonate remains unaffected.

The Breakdown of Magnesium Carbonate

Magnesium carbonate, represented by the chemical formula MgCO₃, is a compound with a molar mass of 84.3145 g/mol. When exposed to heat, it undergoes a chemical transformation. The lower bond energy within magnesium carbonate plays a significant role in its behaviour when heated. As the temperature rises, the bonds holding the carbon dioxide and magnesium oxide molecules together weaken, leading to the breakdown of magnesium carbonate into its component parts.

The Stability of Sodium Carbonate

On the other hand, sodium carbonate (Na₂CO₃) exhibits a distinct behaviour when subjected to heat. This compound possesses a higher bond energy compared to magnesium carbonate. The robustness of these bonds prevents sodium carbonate from breaking down under the influence of heat. As a result, even when heated, sodium carbonate retains its structural integrity and remains unchanged.

Contrasting Factors

To summarize, the dissimilarity in bond energies is the key factor that sets apart the behaviour of magnesium carbonate and sodium carbonate when exposed to heat. While the lower bond energy of magnesium carbonate makes it susceptible to breaking down into carbon dioxide and magnesium oxide, the higher bond energy of sodium carbonate ensures its stability and resistance to heat-induced changes.

Conclusion

In conclusion, the divergent responses of magnesium carbonate and sodium carbonate to heating can be attributed to the differences in their bond energies. This phenomenon highlights the intricate nature of chemical compounds and their behaviour under varying conditions. By understanding these nuances, we gain insights into the fascinating world of chemical reactions and transformations.

Q155:

It is also possible to detect the presence of SO₂ with lime water. Why?

A155:

Sulphur dioxide (SO₂ or O₂S) is a gas that has no visible colour but a very strong smell. Under high enough pressure, it becomes a liquid and easily dissolves in water. Coal and oil burning at power plants, as well as copper smelting, are major contributors of airborne sulphur dioxide. Volcanic eruptions are a natural source of sulphur dioxide releases.

SO2 gas makes lime water look milky because it makes solid calcium sulphite.

Ca(OH)₂ + SO₂ –> CaSO₃ + H₂O

When too much SO2 is passed, the white milkiness goes away.

CaSO₃ + SO₂ + H₂O –> Ca(HSO₃)₂  [Solution is colourless]

Q156:

The crack in our tooth can be repaired using Sorel cement. Why?

A156:

Sorel cement, or zinc hydroxy chloride [Zn(OH)Cl], is a chemical compound. Due to the quick transformation of Zn(OH)Cl to ZnO, it is used for repairing cracks in teeth.

Zn(OH)Cl = ZnO + HCl

ZnO is useful for repairing tooth fractures.

Q157:

ZnCl₂.2H₂O does not become anhydrous ZnCl₂ on heating.

A157:

ZnCl₂.2H₂O when heated in air decomposes to their oxides.

When heated: ZnCl₂.2H₂O –> Zn(OH)Cl + HCl + H₂O

When heated: Zn(OH)Cl –> ZnO + HCl

Hence ZnCl₂.2H₂O does not become anhydrous on heating.

Q158:  

Why is Plaster of Paris a Popular Choice for Mould Casting?

A158:

Introduction

The practice of using Plaster of Paris for mould casting is widespread due to its exceptional qualities and versatility. In this discussion based answer, we will delve into the reasons behind the common use of Plaster of Paris for creating moulds.

Unique Attributes of Plaster of Paris

Plaster of Paris, scientifically known as calcium sulphate hemihydrate, is a gypsum-based plaster celebrated for its rapid drying capabilities. Originating from plentiful gypsum deposits in the Paris region, this plaster takes the form of a fine white powder. Over the course of history, Plaster of Paris has gained popularity across various fields.

Maintaining Structural Integrity

A key factor driving the selection of Plaster of Paris for mould casting is its remarkable ability to maintain its shape and structural integrity during the drying process. Unlike many other materials, Plaster of Paris does not succumb to shrinking or cracking as it dries. This property makes it an ideal medium for crafting intricate moulds with fine details and complex contours.

Wide Range of Applications

Plaster of Paris's utility extends beyond mould casting, finding a place in diverse applications. Notably, it has been extensively used to create intricate plasterwork that embellishes ceilings and borders. Its dependable strength ensures the longevity of such plasterwork, enhancing the visual appeal of architectural designs.

The Manufacturing Process

The production of Plaster of Paris involves heating gypsum, or calcium sulphate dihydrate, within the temperature range of 120 to 180 degrees Celsius (248 to 356 degrees Fahrenheit). Controlled heating triggers chemical changes in the gypsum, resulting in the formation of the hemihydrate form, which serves as the basis for Plaster of Paris.

Fire Resistance

In addition to its applications in casting and decoration, Plaster of Paris possesses a practical attribute. By incorporating additives that slow down its setting process, Plaster of Paris can act as an effective passive fire barrier within interior spaces. This fire-resistant characteristic adds to the material's versatility, making it an invaluable asset for various construction and safety-related purposes.

Conclusion

In conclusion, the distinctive qualities of Plaster of Paris, characterized by its resistance to shrinking, rapid drying, and fire resistance, contribute to its popularity as a material for mould casting and various other uses. Its historical significance and practical advantages ensure its continued relevance in industries seeking reliable and adaptable materials for both artistic and functional applications.

Q159:  

Why Does Red Litmus Paper Change to Blue in the Presence of Lime Water?

A159:

Introduction

The phenomenon of red litmus paper transforming into blue upon contact with lime water presents an intriguing insight into chemical interactions. In this discussion based answer, we will uncover the reasons behind this colour shift and explore the role of litmus paper as a pH indicator.

Litmus Paper: A Tool for pH Measurement

Litmus paper is a valuable pH measurement tool created by impregnating filter paper with a solution of litmus. Derived from lichen, litmus offers a red colour response to acidic environments and a blue colour reaction in the presence of bases.

Varieties of Litmus Paper

Litmus paper is available in various types, each designed to convey specific pH information:

• Purple Litmus Paper: It takes on a purple hue at pH 7, turns red under pH 4.5, and transitions to blue beyond pH 8.3.
• Blue Litmus Paper: Under standard pH conditions, it remains blue or may shift slightly towards purple. However, it turns red at pH levels below 4.5 and retains its blue colour at pH levels above 8.3. If the blue paper remains unchanged, it indicates a basic substance.
• Red Litmus Paper: At pH-neutral levels, it remains red or may change slightly to purple. Below pH 4.5, it becomes red, while above pH 8.3, it shifts to blue. If the red litmus paper maintains its original colour, it signifies an acidic substance.

Interpretation of the Litmus Test

The litmus test is a simple method used to categorize liquids or gases as acidic, neutral, or basic. It distinguishes between pH levels below 4.5, between 4.5 and 8.3, and above 8.3. However, the litmus test is not intended for precise pH measurements.

Lime Water's Impact

The transformation of red litmus paper to blue in the presence of lime water can be attributed to the alkaline nature of lime water, which contains a solution of calcium hydroxide in water. This alkalinity raises the pH level of the litmus paper from an acidic range to a basic range, leading to the colour change.

Conclusion

In conclusion, the captivating change of red litmus paper to blue when exposed to lime water is a manifestation of the inherent properties of litmus as a pH indicator. This colour alteration not only highlights chemical reactions but also underscores the significance of litmus paper in discerning between acidic, neutral, and basic substances.

Q160:  

Neutrality is in barium chloride solution. Why?

A160:

Barium chloride is a compound composed of barium and chlorine. It is commonly used in laboratories to test for sulphate ions and has various industrial applications, such as purifying brine solutions in caustic chlorine plants. It's also used in creating heat treatment salts, reinforcing steel surfaces, producing pigments, and creating colourful explosions. Barium, an alkaline earth metal denoted by the symbol Ba and atomic number 56, doesn't occur naturally in its pure form due to its reactivity. It forms compounds with elements like sulphur, carbon, and oxygen to create minerals.

The neutrality of barium chloride solution arises from its behaviour when dissolved in water. Upon interaction, BaCl₂ undergoes a reaction, breaking down into strong bases (Ba(OH)₂) and strong acids (HCl):

BaCl₂ + 2H₂O → Ba(OH)₂ + 2HCl

This reaction results in the simultaneous production of acidic and basic components, effectively cancelling out each other's effects. As a result, barium chloride solution becomes neutral.

Q161:  

To create a pure white paint, ZnO is used.

A161:

Paint formulation involves the intricate blending of diverse elements: pigments, resins or binders, solvents, and chemicals. These paints serve a myriad of purposes, adorning indoor and outdoor surfaces like walls, cars, and furniture. Their composition varies according to the substrate—be it concrete, brick, stone, wood, metal, or glass—addressing specific needs such as aesthetics, shielding against radiation, moisture, microbes, fire, and heat insulation. Paints manifest as either water-based or oil-based, each boasting distinct characteristics. In this intricate mixture, Zinc Oxide (ZnO) assumes a pivotal role, especially in primers and outdoor paints, contributing to mildew resistance, corrosion prevention, and stain blockage.

At the heart of crafting pure white paint resides the primary white pigment—Zinc Oxide, often dubbed zinc white or Chinese white. In the realm of art, zinc oxide stands as one of the three primary white pigments, joining the ranks of lead and titanium whites. A remarkable trait of zinc oxide lies in its steadfast color retention when exposed to light, ensuring that paints incorporating this pigment, whether in watercolours or oil-based media, retain their inherent whiteness. Furthermore, when integrated into oil-based paints, zinc oxide exhibits reduced proclivity for yellowing in comparison to other oil-blended white pigments. The reaction between zinc oxide and fatty acids in drying oil culminates in the formation of zinc soaps, bolstering the hardness of the paint film.

Cautious consideration is required when employing zinc white in oil paintings, as even minute quantities of zinc oxide can render the oil paint film more brittle, rendering it susceptible to peeling. Exposure to near ultraviolet light accelerates the generation of hydrogen peroxide, which contributes to the chalky appearance and fragmentation of the oil paint film.

Zinc oxide demonstrates an oil absorption ratio akin to that of talc, encompassing a spectrum from 20 to 25%, contingent on the size and morphology of particles. Innovative manufacturing methodologies facilitate the production of pigments necessitating lower oil content, potentially as low as 14–15% for paste grades. Zinc oxide presents an array of advantages, encompassing UV light absorption, fortification of the paint film, augmented water resistance, counteraction of detrimental acids, and the enhancement of coatings with superior biocidal, colour-retaining, and durability attributes.

Notably, ZnO stands as a refractory oxide, boasting outstanding heat resistance and exceptional resistance to corrosion. It is these very attributes that designate it as the quintessential ingredient for formulating white paint, culminating in not only visual allure but also the enduring longevity of the painted surface.

Q162:

What does the term "precipitation titration" refer to?

A162:

If you have ever put a solid (like sand) into a clear liquid (like water), you have probably seen a solid sitting there without dissolving. But in some reactions, the slow addition of liquid makes a solid form and build up, as if by magic.

Obviously, most everyday liquids don't mix to make solids. But when they do, and the chemical reaction that caused it is known, the amount of product made can be used to figure out how much of the reactant was in the solution before a second reactant was added to start the reaction that made the solid.

This kind of change from liquid to solid is called precipitation (not to be confused with weather), and precipitation titrations are a type of reaction used all over the world in many businesses. They are helpful because they make it possible to find the end point of a response very precisely. With old methods, this point would have to be found by eye.

What Does Titration Mean?

You can calculate the total number of reacting molecules in a solution by knowing its concentration and chemical makeup.

If you have a solution of a second substance but don't know its concentration but do know its volume, you can determine the concentration of the analyte by gently adding the substance of known concentration (the titrant) until the solution is empty.

Precipitation Titration Indicators

Indicators for titrations of precipitation fall into three main categories. One searches for silver cations and two for chloride ions.

(1) The Mohr's method is a technique for determining the concentration of chloride in a solution using precipitation titration; it was developed in 1855 by Karl Mohr. Using silver nitrate (AgNO₃) as a titrant, this technique falls under the category of argentometric titration (where the silver(1) ion is employed).

The titrant-analyte solution is adjusted by adding potassium chromate, or K₂CrO₄. The formation of a reddish-brown Ag₂CrO₄ precipitate marks the end point of the titration.

(2) The Volhard technique utilises potassium thiocyanate (KSCN) as the titrant in the determination of silver ions. The development of the reddish-brown Fe(SCN)²⁺(ferrous thiocyanate) marks the end of the type in which iron ions (Fe³⁺) are added to the solution.

(3) Chloride can be measured with the Fabans method, which employs Ag⁺ as a titrant once again. For example, when the greenish-yellow dye dichlorofluorescein is introduced to the solution, the precipitate's positive charges on the surface attract the silver cations, causing the dichlorofluorescein to change colour from green to pink.

Q163:

Simply put, what does the term "normal solution" mean?

A163:

Another method for quantifying the concentration of a solution is referred to as normality (N). It is very similar to molarity, but instead of the Gramme Molecular Weight (GMW) that is represented in molarity, it uses the gram-equivalent weight of a solute to express how much of that solute there is in one litre (L) of solution. This is how it differs from molarity.

A 1N solution is one that has a solute concentration that is equivalent to one gramme per one litre of solution.

When expressing weight in terms of grammes equivalent, it is necessary to take into account the valence of the solute.

Valence is a reflection of an element's combining power, which is frequently assessed by the number of hydrogen atoms it is able to displace or combine with. Valence can be positive or negative.

The amount of a material that can replace or mix with one hydrogen atom is the gram-equivalent weight of that substance. This weight is equal to 1.0 grammes.

Example:

To find the weight of a substance in grammes equivalent, divide the formula weight of a solute by its valence (the amount of hydrogen ions that can be displaced). This will give you the gram-equivalent weight of the material.

Normality of a 1.0-liter NaCl solution containing 1.0 gram-equivalent weight is the GMW of NaCl divided by its valence:

(the atomic weight of sodium is 22.99 and that of chlorine is 35.45)

GMW of NaCl = 22.99 + 35.45 = 58.44 g

N = GMW/valence (NaCl has a valence of 1.0).

58.44 g/1.0 = 58.44 g = 1.0 grammes of NaCl equivalent = 1N solution of NaCl

Because NaCl has a valence of one, the molarity and normality of the solution are identical in this instance.

Q164:  

Can you explain the meaning of the term "molar solution"?

A164:

The concept of molar solution revolves around expressing the concentration of a solution in terms of molarity. Molarity serves as a common metric to quantify the concentration of solutes within a solution. To comprehend the notion of a molar solution, one must consider the gram molecular weight of the solute and its relationship to the volume of the solution.

The "formula weight" of a substance is synonymous with its gram molecular weight (GMW). This value corresponds to the sum of the atomic weights of all constituent atoms within the molecule, measured in grams. For instance, the GMW of NaCl is calculated by adding the atomic weight of Na (22.99) to that of Cl (35.45), summing up to 58.44 g. These atomic weights are conveniently accessible through the periodic table or labels on the substance's container.

A 1 molar (M) solution signifies that within 1 liter (L) of the solution, the mass of the solute equals its GMW. As an illustration, a 1M solution of NaCl implies that 58.44 g of NaCl are dissolved in 1 liter of water.

In practical scenarios, such as enzyme histochemistry, specific substances like hydrochloric acid (HCl) and buffer solutions like sodium dihydrogen phosphate (NaH2PO4) are employed. The GMW of HCl can be determined by summing the atomic weight of hydrogen (H) and chlorine (Cl), culminating in 36.45 g. Similarly, for NaH2PO4, the GMW is calculated considering the atomic weights of sodium (Na), hydrogen (H), phosphorus (P), and oxygen (O), resulting in a GMW of 119.98 g.

A convenient formula can be employed to swiftly ascertain the required weight of a substance for a specific molar solution:

Weight in grams = desired molarity × required volume in liters × GMW,

OR

W = M × V × GMW.

Q165:  

In simple terms, what does the term "molal solution" mean?

A165:

The concept of a "molal solution" refers to a solution's molality (m), which is a measure of concentration. It is calculated by dividing the amount of solute moles by the amount of solvent in kilograms. For instance, a "one-molal" solution of sodium chloride would contain one mole of NaCl dissolved in one kilogram of solvent, usually water. The term "m" is used to represent molality.

The distinction between molality and molarity lies in their respective units of measurement. Molality is expressed in terms of kilograms of solvent, while molarity is expressed in terms of liters of solution. Molality is particularly useful for studying properties of solutions that depend on factors like vapor pressure and temperature, as its value remains constant across different temperatures. On the other hand, molarity can be slightly affected by changes in temperature due to the volume of the solution being temperature-dependent.

Example:

Consider a scenario where one mole of sucrose (equivalent to approximately 342.3 grams) is dissolved in precisely one liter of water. As the solute dissolves, the result is a solution of sugar water. If we add more water while dissolving the solute and ensure thorough mixing, what would be the molality of the resulting solution? Remember that the mass of one liter of water is one kilogram (since the density of water is 1.00 g/mL and there are 1000 mL in a liter). Thus, the calculation would be:

Molality = 1.00 mol / 1.00 kilogram

The correct answer is 1 mol/kg.

Similarly:

If two moles of solute were dissolved in one kilogram of solvent, what would be the molality?

Molality = 2.00 mol / 1.00 kg

The answer is 2.00 mol/kg.

It's important to note that the concept of molality is independent of the specific substance being dissolved. Regardless of whether the solute is sucrose, sodium chloride, or any other substance, one mole of any substance contains approximately 6.02 x 10²³ units (Avogadro's number).

Q166:

A solution of sulfuric acid that has a volume of one litre and contains 571.4 grammes of H₂SO₄ per litre of solution has a density of 1.329 grammes per cubic centimetre. Determine the molality of the H₂SO₄ in this solution.

A166:

1 litre of solution is equivalent to 1000 millilitres, or 1000 cubic centimetres.

1.329 g/cm³ multiplied by 1000 cm³ equals 1329 g, which is the total mass of the solution.

Subtracting 571.4 grammes from 1329 grammes results in 757.6 grammes, which is equal to 0.7576 kilogrammes (the mass of water in the solution).

571.4 grammes divided by 98.0768 grammes per mol equals 5.826 mol of H₂SO₄

5.826 mol / 0.7576 kg = 7.690 m

Q167:

The density of a solution of H₂SO₄ with a molal concentration of 8.01 g/mL is 1.35 g/mL. What is this solution's molar concentration?

A167:

8.010 m is equivalent to 8.010 mol/kg of solvent (98.0768 g/mol) = 785.6 g of solute.

In the 8.010 m solution, the total amount of solute and solvent is 785.6 g plus 1000 g, or 1785.6 g.

1785.6 g divided by 1.354 g/mL equals 1318.76 mL 

8.01 molecules divided by 1.31876 L equals 6.0739 M 

6.074 M (to four significant figures).

Q168:

What exactly are "primary standard substances"?

A168:

Substances that do not change chemically when exposed to the elements of the air (O₂, CO₂, etc.) are considered the primary standard substances. The most common types of standards are salts and oxides of metals.

A primary standard is an extremely pure, consistent, water-free, and molecularly heavy reagent. A substance's concentration can be accurately measured with the help of standards. They serve as a standard against which other concentrations can be calculated and analytical tools can be validated.

Here are some significant examples of the primary standard:

(1) Sodium Carbonate (Na₂CO₃)

(2) KHP stands for potassium hydrogen phthalate (KHC₈H₄O₄).

(3) Potassium dichromate (K₂Cr₂O₇)

In chemistry, the primary standard is a substance that is always the same and easy to get. Among the things that make up the primary standard are:

(1) Very pure

(2) Stability (little change)

(3) Low ability to hold water and bloom

(4) If it's used in a titration, it's easy to dissolve

(5) The same amount of weight

Q169:

Exactly what do you mean by the term "secondary standard substances"?

A169:

Secondary Standard Substance refers to substances that cannot be stored in an open environment and quickly react with the air's constituents (O₂, CO₂, etc.) during the weighing process. Secondary Standard Substances include, for example, HCL, H₂SO₄, NaOH, KOH, and KMnO₄.

A secondary standard is a standard set up in the laboratory for a particular analysis. It generally does not remain constant, and its concentration typically decreases over time, so measurements taken with high precision during preparation will not hold up. Typically, it is compared to a primary standard.

Sodium hydroxide (NaOH), a chemical used as a base, is an example of a secondary standard.

Water (H₂O) from the air can be easily absorbed by commercially available NaOH, which also contains impurities such as sodium chloride (NaCl), sodium carbonate (Na₂CO₃), and sodium sulphate (Na₂SO₄). A primary standard weak acid, like potassium hydrogen phthalate, is used in a titration to measure the concentration of NaOH in a solution.

Q170:

Electrode potential is what exactly?

A170:

Electrode potential is the voltage or potential difference between a standard hydrogen electrode and the given electrode whose potential is being described. It is the difference in potential between a point on the electrode surface and a point in the bulk of the solution. This difference is caused by the movement of charged particles and the sticking of some polar molecules to the electrode surface.

The normal hydrogen electrode is always at zero potential because that's what people usually do.

Electrode potential has uses such as:

(1) Prediction of chemical or electrical processes related to corrosion

(2) Used to pick substances and gadgets for controlling reactions

(3) Helps study crevice corrosion and pitting, since electrode potential in cracks and holes is studied to figure out how to control reactions.

The potential of an electrode is measured in Volts. Cu²⁺ has a standard electrode potential of +0.34 volts.

Consider the atom of chlorine. You are aware that Chlorine has seven electrons in its outermost electron shell and needs only one more to have a stable outer electron shell. This indicates that Chlorine has a strong tendency to gain 1 electron and exist in the oxidation state of -1. Standard Electrode Potential is a measurement of a species's ability to acquire or lose an electron; therefore, Chlorine has a high Standard Electrode Potential.

Cl₂ + 2e^- <=> 2Cl^-

The E° for chlorine is +1.36V.

Q171:

Strong concentrations of HNO₃ have no effect on aluminium. Why?

A171:

Oxidising properties are seen in concentrated HNO3. It converts aluminium to aluminium oxide. As a result of its oxides forming a protective layer, Al becomes inactive. As a result, it doesn't react with concentrated HNO₃.

Q172:

The electrolysis of alumina can be improved by including cryolite. Why?

A172:

Cryolite is utilised in the electrolysis of aluminium oxide as it aids in the economically feasible extraction of aluminium. Cryolite, or sodium aliminium fluoride, is a chemical element. In the production of aluminium, it is combined with bauxite. The high melting point of aluminium oxide is 2030 degrees celsius. The Hall-Héroult method makes it hard to refine aluminium. When cryolite is added, the melting point of the mixture changes to 1000 degrees Celsius. Cryolite can also work as a cleaner. It makes the liquid bauxite solution flow more easily. So, cryolite helps remove aluminium in an economically feasible way.

Q173:

Heating Hg(NO₃)₂ produces Hg and HgO. Why?

A173:

When heated, Hg(NO₃)₂ produces Hg rather than HgO because HgO is an unstable oxide and quickly breaks down into Hg and O₂ upon contact with heat.

2Hg(NO₃)₂ –> 2Hg + 4NO₂ + 2O₂

Q174:

Group II B does not contain elements with variable valency. Why?

A174:

The d-subshell of elements in group IIB is full (d¹⁰), and no electrons are available for valency. Therefore, these elements lack variable valency.

Q175:  

Aircraft manufacturers rely on aluminium for a variety of components. Why?

A175:

Aluminium finds extensive usage in the transportation sector, accounting for approximately 27% of its total applications. With its silvery-white appearance and soft, ductile properties, aluminium, a member of the boron group of elements, boasts a wide range of uses. However, it is particularly prominent in the aerospace industry, being a prevalent material in aircraft manufacturing.

The preference for aluminium in aircraft construction is attributed to its combination of lightweight nature, corrosion resistance, and strength. Aluminium offers an advantageous blend of affordability, reliability, low weight, and durability. While materials like steel and iron exhibit greater strength compared to aluminium, this factor alone doesn't dictate its use in aerospace. The significant weight differential is a crucial factor. Both steel and iron are notably heavier than aluminium, which can adversely affect an aircraft's performance during take-off and flight.

It's important to note that aircraft are not exclusively constructed from aluminium. Carbon-alloy steel is another common choice for aerospace applications. The introduction of carbon enhances the strength and oxidation resistance of steel. Titanium is another metal frequently employed in aircraft engineering due to its inherent corrosion resistance, lightweight properties, and high strength. Manufacturers often alloy titanium with iron or manganese when fabricating airplane frameworks and engines. Nevertheless, the demand for these metals generally remains lower than that of aluminium. Despite not being the most robust metal, aluminium boasts an exceptional strength-to-weight ratio, making it well-suited for aviation purposes.

Q176:

Thermit welding makes use of aluminium. Why?

A176:

Thermite welding is a highly developed welding technique that uses an exothermic reaction to unite metal parts. Aluminium powder and iron oxide (rust) are used in this reaction. In this reaction, the aluminium powder serves as fuel, while the iron oxide plays the role of an oxidant. When an electric spark is applied to this mixture, it reacts with itself, producing such high temperatures that the two metals melt and fuse together.

Aluminium is well-suited for thermite welding because of its many desirable features. To begin with, its high melting point (660°C; 1,220°F) makes it a prime candidate for thermite's reaction, which generates extraordinarily high temperatures. Second, heating aluminium causes it to spark, which both initiates and sustains the reaction. Finally, once molten, aluminium possesses powerful bonding qualities that will hold the two pieces of metal together as they cool. Last but not least, aluminium is cheap in comparison to other metals; therefore it won't blow your budget.

Q177:

Magnesium is utilised as an absorbent for nitrogen. Why?

A177:

Together with nitrogen, magnesium quickly forms nitride; hence,

3Mg + N₂ –> Mg₃N₂

It's put to use in nitrogen absorption processes.

Q178:

Overhead power cables frequently make use of aluminium. Why?

A178:

One of the greatest advancements in human history is the invention of electricity. It sets our earth in motion, enabling for instantaneous communication across continents. There could be no modern scientific or technological progress without electricity. And without power, there would be no way to manufacture aluminium. It's fascinating that this metal is responsible for power transmission across such vast distances nowadays.

Only copper, and only by 33%, is a superior base metal than aluminium, but aluminium has one clear benefit: it is lighter.

Even though aluminium wire is 1.5 times lighter than copper wire, it can carry the same amount of current. When it comes to long-distance power transmission via high-voltage power lines, weight is one of the most crucial considerations. This is why all primary power lines use aluminum-based conductors.

Q179:

In chemistry, Al is known as an amphoteric element. Why?

A179:

If a substance is amphoteric, it will react with both acids and bases. As it reacts with both acids and alkali, aluminium is considered amphoteric.

2Al + 6HCl –> 2AlCl₃ + 3H₂

2Al + 2NaOH + 2H₂O –> 2NaAlO₂ + 3H₂

Q180:

How come the melting and boiling points of ‘Boron’ are so high?

A180:

Boron (B) can be found in two different physical forms: a brown powder and a crystalline silvery black solid. Is located in Group 13 of the periodic chart and has the symbol B. Its atomic number is 5. It's a metalloid; therefore it possesses characteristics of both metals and non-metals.

At 2200 degrees Celsius, boron will melt and become a liquid.

The boiling point of boron is 2550 degrees Celsius, at which point it becomes a gas.

Boron has an electronegativity of 2.04. The electronegativity of an atom is a quantitative measure of its ability to attract and retain bonding electrons.

Heat of Vaporisation for boron is 489.7 kJ/mol.

Since boron's atoms are more strongly bound to one another in both its solid and liquid states, it has a high melting and boiling point.

Q181:

It is possible to obtain AlCl₃ in its dimeric state. Why?

A181:

A trigonal planar structure characterises AlCl₃. An aluminium atom has three sp₂ hybridised orbitals that connect to chlorine atoms. The bond angle is a full 120 degrees. In order to complete their valence shells, chlorine atoms give up one of their electrons to aluminium in a chemical connection. Due to the sharing of electrons with the three chlorine atoms, aluminium, which has three of its own, gains a total of three, bringing its valence electron count to six. Two additional electrons are needed by aluminium to finish filling out its outer electron shell. Chlorine possesses 3 pairs of electrons that aren't involved in bonds, making a total of 6. As a result of this process, two AlCl₃ molecules dimerize, therefore completing the valence electron shell of aluminium. Dimer Al₂Cl₆ is formed when one chlorine atom from each molecule donates an electron pair to the aluminium nucleus, creating a dative covalent bond.

Q182:

There is a high melting point for diamond. Why?

A182:

Since it is so uncommon, diamond is both extremely valuable and costly. Diamonds are extremely rare yet do occur naturally. They are extracted from mines in South Africa and Brazil. They have also been discovered in meteorites (rocks) that have crashed on Earth. Diamonds can also be synthesised in a lab.

Diamond, with its few drawbacks and much strength, is the ultimate gemstone. It's common knowledge that diamonds are the hardest natural substance, but fewer people know that diamonds are also four times as hard as the next hardest natural mineral, corundum (sapphire and ruby). However, despite its toughness, it is not unbreakable.

A diamond can be broken in half along any of its four cleavage directions if struck with sufficient force.

Covalent bonding is what gives diamond its massive covalent structure. Diamond has the greatest melting point because breaking the extremely strong covalent bonds requires a great deal of energy.

Q183:

Aluminium sulphate solution in water is acidic. Why?

A183:

Aluminium sulphate, when mixed with water, breaks down into Al(OH)₂ and H₂SO₄.

Al(SO₄)₃ + 6H₂O –> 2Al(OH)₃ + 3H₂SO₄

H₂SO₄ is a strong acid, producing high concentrations of H⁺ ions, while Al(OH)₃ is a weak base, producing just a small amount of OH^- ions. Therefore, Al₂(SO₄)₃ in water is an acidic solution.

Q184:

The hydroxide of aluminium is an amphoteric hydroxide. Why?

A184:

Hydroxides are chemical substances that have a hydroxyl group in them. They can be acidic, alkaline, or basic.

Aluminium, zinc, chromium, and a few other metals have hydroxides that dissolve in both acids and alkalis. These substances are called amphoteric hydroxides.

Aluminium is both a chemical element and a technical grade material, thus it is important to distinguish between the two. The former is one of the most fundamental elements of Earth's crust and is abundant in the natural world. Bauxite, an ore consisting of aluminium hydroxides and metal oxides (iron, silicon, etc.), is a common raw material used to create aluminium of technical grade.

It is possible to create large quantities of Al(OH)₃ in the lab, and aluminium hydroxide can be produced by reacting an aluminium salt solution with ammonia or sodium hydroxide.

Aluminium oxides are produced only when aluminium salts react with more powerful compounds, such as hydroxides or others.

In what ways is aluminium hydroxide unique?

White and odourless, Al(OH)₃ is insoluble in water and has no taste. It turns into alumina and has amphoteric characteristics when heated.

When we say that aluminium hydroxide is amphoteric, what exactly do we mean?

What this means is that the compound's acid/base behaviour depends on the pH of the surrounding environment. That is, Al(OH)₃ responds to both acids and bases.

The industrial methods utilised to create this chemical have a significant impact on its qualities. Long-term storage of Al(OH)₃ powder, for instance, makes it more challenging to treat with acids or bases. A gel of aluminium hydroxide can be broken down in either an acidic or basic environment.

Q185:

When sufficient NaOH solution is added to an aqueous solution of aluminium chloride, a gelatinous (thin) precipitate is first generated, which then becomes transparent. Why?

A185:

A gelatinous precipitate of Al(OH)₃ is created when NaOH solution is added drop-wise to an aqueous AlCl₃ solution; this precipitate dissolves in excess NaOH solution and produces a colourless solution of sodium aluminate.

AlCl₃ + 3NaOH –> Al(OH)₃ + 3NaCl            (White gelatinous precipitate)

Al(OH)₃ + NaOH –> NaAlO₂ + 2H₂O           (Sodium aluminate solution)

Q186:

Electrodes are often constructed from graphite. Why?

A186:

If we want to know why electrodes are often made of graphite, we need to look at how graphite is put together. In graphite, the carbon atoms are grouped in layers, and covalent bonds hold them together to keep their shape. The number of electrons that are not in one place is an important part of graphite's structure. Graphite only needs three of its outer-energy electrons to join. This leaves the fourth electron free to act in a way that is not tied to a specific place. Electrons that aren't tied to a specific atom and can move around easily are said to be ‘delocalized’. Because of these electrons, graphite has a high amount of conductivity, which is why it is often used as an electrode.

Graphite is often used for electrodes because it is a good conductor and has a few other useful properties. Graphite has a very high melting point, so it can be used to carry electricity in high-temperature reactions without changing state. Graphite is so stable that it can be used in places where other materials would not work.

Another answer to the question "Why is graphite used in electrodes?" has to do with how common and how much it costs.

Graphite can be made in a lab, and there are also large amounts of it all over the world that are mined. Graphite is used to make electrodes because it is easy to get and has the properties that electrodes need. It is also a cost-effective and convenient choice, which is another reason why it is used.

Electrodes can be made of anything that moves electricity. Graphite or valuable metals like gold, silver, or platinum can be used to make electrodes, depending on what they will be used for. People also often use copper, titanium, and brass.

Synthetic graphite electrodes can be made from many different materials that contain carbon. Some of these are acetylene, coal, and petrochemicals. Extreme heating changes the carbon in these substances into graphite's characteristic structure. For graphite to form, the carbon must be heated to more than 3000°C. This is known as graphitization.

Because graphite has electrons that are spread out in its structure, it conducts electricity very well. When graphite is used to make electrodes, it is mainly for its ability to carry electricity.

Q187:

Why does carbon stand out from the other members of Group IV A?

A187:

The elements of Group IV-A can be found roughly near the centre of the periodic table. Carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and ununquadium (Uuq) make up what is now known as group 4A (or IVA or group 14) of the current periodic table.

The way these elements are set up shows that they have four electrons in their outermost (valence) shell. Two of these electrons are in s–orbital, and the other two are in p–orbital. Because of this, the valence shell of these elements has a s²p² structure. The last shell of C, Si, and Ge is made up of s² electrons, s²p⁶ electrons, and s²p⁶d¹⁰ electrons, respectively. This shows how carbon is different from silicon and how silicon is different from the other elements in this subgroup.

Carbon is different from other elements in the following ways:

(1) It can only have four co-ordination numbers because it doesn't have any d-orbitals in its second shell.

(2) Because it is the only element that can form multiple bonds, like C=C, C=O, C=S, and C=N.

(3) In the way that its marked ability links to other abilities.

Q188:

The muddiness of water (say, from any pond) can be removed with alum. Why?

A188:

Water that is dirty and cloudy is not only ugly, but it can also be bad for creatures that live underwater. Even though sport fish are rarely killed directly by high silt loads in ponds, muddy water can make it hard for fish to grow. When there is a lot of suspended material in ponds, it can cause the following problems:

(1) Low sunlight means less organism’s production,

(2) Less dissolved oxygen,

(3) Higher water temperatures,

(4) Fish eggs and young dying from suffocation,

(5) Less fish food,

(6) Less clarity,

(7) Less fish growth,

(8) Fish with a bad taste, and

(9) Less water in the pond.

If everything else is the same, ponds with clear water can have a lot more fish than ponds with dirty water. Muddy water makes it harder for fish to find food and makes it harder for them to see and catch it. Muddy water is a good place for blue-green algae and germs to grow, which can make the water and fish taste bad. Most of the time, algae are to blame for green water, which is a different kind of trouble with a different solution.

Most of the time erosion of soil leads to muddy ponds. Heavy rains and strong winds move damaged soil from misused fields, open shore lands, and agricultural land without protection into ponds. Any area of empty space is a place where soil loss can start.

Muddy ponds can be cleaned by using chemicals that bond and separate mud and other particles, taking them out of water solutions. Putting alum (aluminium sulphate) on the surface of the pond has been shown to work.

But alum can lower the pH and make the water more acidic. In soft water (less than 20 mg calcium carbonate), it should be used with limestone (in a ratio of 1:0.5 alum to calcium carbonate) to keep the acidity from changing too much.

When water is added to alum, it breaks down into Al(OH)₂, which helps settle the mud-like impurities in the water. Because of this, it is used to clean up dirty water.

Q189:

Aluminium is a common de-oxidizer in the steel making process. Why?

A189:

When oxygen is removed from molten metal, the process is called de-oxidation. The process calls for the addition of oxygen-loving components, the oxides of which are either gaseous or quickly transform into slags.

Typically, Mn, Si, and Al are added to steel in order to de-oxidize it, while Cr, V, Ti, Zr, and B are also occasionally used.

A contradiction is displayed during de-oxidation of molten steel. When the de-oxidizer concentration in the melt is raised over a threshold amount, re-oxidation of the steel occurs.

Except for the acid-silicon reducing process, all methods of making steel require de-oxidizing the steel once it has reached the right amount of carbon. This makes the dissolved oxygen inactive and stops carbon from being oxidised further.

Steel de-oxidation mainly uses three elements:

(1) Manganese and silicon (as low-carbon ferro alloy or silico-manganese alloy); and

(2) Aluminium (that is about 98% pure).

Aluminium is frequently used as a de-oxidizer in the steelmaking process because of its efficiency.

Because it removes all oxygen and nitrogen from steel, Al is commonly used as a de-oxidizer in the steel industry. This results in the formation of Al₂O₃ and AIN.

4Al + 3O₂ –> 2Al₂O₃

2Al + N₂ –> 2AlN

Q190:

Heating hydrated aluminium chloride (AlCl₃.6H₂O) does not produce anhydrous aluminium chloride. Why?

A190:

When subjected to high temperature; hydrated aluminium chloride changes into aluminium oxide, Al₂O₃. Hence, heating hydrated aluminium chloride (AlCl₃.6H₂O) does not produce anhydrous aluminium chloride.

2AlCl₃.6H₂O –> Al₂O₃ + 6HCl +9H₂O

Q191:

How can the E^o value help in determining the oxidising and reducing potential of a substance? Order the following oxidising and reducing agents from weakest to strongest:

Cl^-, Cu, H2, H^-, HF, Pb, and Zn are all reducing agents.

Cr³⁺, Cr₂O₇^2-, Cu²⁺, H⁺, O₂, O₃, and Na⁺ are all oxidising agents.

A191:

When the oxidation potential goes up, the reducing strength of the reducing agent goes up. For the oxidising agent, it's opposite way around. So zinc dioxide is a better oxidizer than sodium.

The reducing agents increase in potency as follows:

HF <  Cl^- < Cu <  H₂ < Pb < Zn < H^-

In the following order, oxidising agents increase in potency:

Na⁺ < Cr³⁺ < H⁺ < Cu²⁺ < O₂ < Cr₂O₇^2- < O₃

Q192:

What exactly does "standard electrode potential" mean?

A192:

In a study comparing the redox reactivity of silver and lead, it was shown that the silver ion, Ag⁺(aq), undergoes spontaneous reduction, but the lead ion, Pb²⁺(aq), does not. In electrochemical cells, the feature known as cell potential provides a straightforward measure of this relative redox activity. In electrochemistry, this characteristic is referred to as cell voltage and represents the energy that is transferred together with the charge. Volts, the SI unit used to quantify potential, are equivalent to one joule of energy per one coulomb of charge. In other words, 1 V = 1 (J/C).

Standard Electrode Potential:

When used in electrochemistry, the cell potential is a way to measure the force that drives a certain type of charge transfer: the transfer of electrons between reactants.

You can't measure the potential of a single electrode or half-cell because electron transfer needs a donor and a receiver, or a reducing agent and an oxidising agent.

Instead, the potential of a half-cell can only be measured in relation to the potential of another half-cell.

So, the difference in potential between two half-cells, E_cell, is the only thing that can be measured. E_cell is described as: E_cell = E_cathode - E_anode, where E_cathode and E_anode are the potentials of two different half-cells working as the cathode and the anode, respectively.

Under standard conditions (1 M concentrations, 1 bar pressures, and 298 K), the potential of a complete cell is equal to the standard cell potential, denoted by the symbol E°_cell.

The potential difference between the cathode and anode halves of a cell, E^o_cell, is equal to E^o_cathode minus E^o_anode.

To make it easy to figure out half-reaction potentials, scientists have chosen one half-cell with a potential of 0V as a universal standard for all cell potential measurements. This half-cell, called the Standard Hydrogen Electrode (SHE), is based on the following half-reaction:

2H⁺(aq) + 2e^- -> H₂(g)

SHE is usually made up of a neutral platinum electrode that goes under in 1M aqueous H⁺ with a stream of bubbling H₂ gas at 1 bar pressure and a constant temperature of 298 K. So, the Electrode Potential (EX) for a half-cell X is the potential recorded for a cell X, which acts as a cathode, and the SHE, which acts as an anode.

E_cell = E_X – E_SHE

E_SHE = 0V (defined)

Therefore,

E_cell = E_X

The standard electrode potential, E^o_X, is equal to the potential of the half-cell X under standard conditions. These potentials are also referred to be Standard Reduction Potentials because cathodes are required for the definition of cell potential.

Q193:

When you say "equivalent weight of an element", what exactly do you mean?

A193:

In simple words, an element's atoms are made up of protons, neutrons, and electrons. The centre, or core, of an atom is made up of protons (particles with a positive charge) and neutrons (particles with no charge).

The electrons go around the centre like planets go around the sun. When electrons from one element combine with electrons from another element, they make new substances called compounds. The electrons that combine are called valence electrons. Valence electrons are those electrons that live in the outermost shell around an atomic centre. Valence electrons are very important because they reveal a lot about the chemical properties of an element, like whether it is electronegative or electropositive, or they show the bond order of a chemical compound, which is the amount of bonds that can be formed between two atoms. Since covalent bonds are made by sharing the electrons in the last shell, the amount shows how many bonds are allowed to form.

Using the information on valence and the atomic weight, which is also on the Periodic Table, it is possible to figure out the comparable weight of each element. On the periodic table, all of the elements are neatly organised from left to right by their atomic number, which is the number of protons or electrons they have.

There are four groups of elements: the main group elements, the transition elements, the lanthanides, and the actinides.

The atomic mass and atomic number can be used to find out what each element is. With these two numbers, you can figure out how many protons, electrons, and neutrons an element has.

Here are a few examples of what the atomic mass and atomic number of atoms in different elements appears like.

(1) There is one proton and one electron in hydrogen. It has a number of atoms of 1 and a weight of 1 as well.

(2) Helium (He) has two protons, two electrons, and two neutrons. It has a number of atoms of 2 and a weight of 4 per atom.

(3) Carbon has six protons, six electrons, and six neutrons. It has a number of atoms of 6 and a weight of 12 per atom.

(4) Oxygen is made up of 8 protons, 8 electrons, and 8 neutrons. It has a number of atoms of 8 and a weight of 16 per atom.

An element's equivalent weight is calculated by dividing its atomic weight by its valence. In other words, it represents the fraction of an element's atomic weight that is attributable to its valence electrons.

Equivalent weight = Atomic weight / Valence

What is the equivalent weight of calcium if its atomic weight is 40.08 and its valence is 2?

Equivalent weight of Ca = Atomic weight of Ca / Valence of Ca = 40.08 / 2 = 20.04

Q194:

For what reason do elements have different "equivalent weights"?

A194:

Atomic weight = valence multiplied by equivalent weight.

While an element's atomic weight is always the same, its valency can change. Therefore, the atomic weight equivalent of an element must change depending on its valency.

CuO (31.77) and Cu₂O (63.54) are two equal forms of Cu in terms of weight.

Q195:  

What does the modern understanding of "atomic weight" entail?

A195:

The concept of atomic weight in modern science refers to the average relative mass of atoms of a specific element compared to the mass of an atom of carbon-12 (¹²C) isotope. This value is expressed as a numerical figure and is commonly denoted as the element's atomic weight.

Q196:

Just what is the law of Dulong Petit?

A196:

Temperature of a Particular Type:

The specific heat of an element is defined as the amount of energy needed to increase the temperature of one mole of the element from 287.5 K to 288.5 K. The SI unit for this is the joule per mole/kelvin.

The atomic heat of an element is calculated by multiplying the element's atomic mass by its specific heat.

The Law of Dulong-Petit:

An element's specific heat multiplied by its atomic mass in the solid state is roughly equal to 6.4. An element's atomic heat is about equivalent to 6.4 if it is solid.

Dulong-Petit's Law has some restrictions:

(1) Elements in their solid state fall under the umbrella of this law.

(2) The heavier element is subject to this law.  Lighter elements with higher melting points are excluded.

(3) This rule provides a rough estimate of atomic weight.

Actions Needed:

Step1: Use any of the methods to calculate the element's equivalent mass.

Step2: Estimate the atomic mass using the formula: “Approximate atomic mass x Specific heat = 6.4”.

Step3: Use the formula: "Approximate atomic mass = equivalent mass x valency" to determine the element's valency.

Step4: The valency of an element is the estimated value rounded up to the closest whole number.

Step5: The corrected atomic mass of an element can be determined using the following formula. Correct Atomic Mass = molar equivalent mass multiplied by valence.

Example:

Find the atomic mass of barium if its equivalent mass is 68.68 and its valency is 2.

Solution:

The equivalent mass of barium is 68.68 grammes, and its valency is 2.

Atomic mass = Equivalent mass x valency = 68.68 x 2 = 137.6

Thus, barium's atomic mass is 137.6.

Q197:

Despite having a higher density than both oxygen and nitrogen, carbon dioxide does not make up the atmosphere's lowest layer. Why?

A197:

Gases in the atmosphere form a uniform mixture due to total diffusion regardless of density. So, although though CO2 is heavier, it is entirely dispersed with lighter gases like oxygen, nitrogen, and so on. This means it doesn't contribute to the formation of the atmosphere's bottom layer.

Q198:  

How does carbon dioxide (CO₂) reach high altitudes in the atmosphere? Rising to higher altitudes typically causes gases to cool and fall due to their specific gravity, around 1.5. At 30,000 feet, for instance, the temperature can be as low as -40 degrees. So, how does some carbon dioxide manage to reach the upper atmosphere despite these conditions?

A198:

It's important to understand that carbon dioxide is a gas, and its behaviour is influenced by temperature and density. As a gas cools down, its density increases. When we move higher up in the atmosphere, the temperature drops, causing gases to become denser. However, the atmosphere's stability is maintained due to the equilibrium between gravity and gas molecules.

Gases, including carbon dioxide, have different molecular weights. CO₂ is heavier than the majority of air molecules, such as oxygen and nitrogen. Consequently, in the Earth's atmosphere, CO₂ molecules tend to settle beneath the lighter molecules. If we apply this concept to various gases, each gas would form distinct layers based on its molecular weight, creating a stratified atmosphere.

To explain further, consider the analogy of a bottle of wine. When the bottle is sealed, both oxygen and carbon dioxide are present in the air, forming separate layers due to their differences in density. The heavier CO₂ forms a layer below the lighter oxygen, preventing exposure to air and maintaining the quality of the wine. Similarly, in the Earth's atmosphere, gases do not form distinct layers because of the kinetic energy of their molecules. Gas molecules spread and fill any available space due to their inherent properties.

In contrast to a sealed bottle, the Earth's atmosphere has vast space and constant movement. Gas molecules experience diffusion, ensuring that gases mix and do not form separate layers. Despite its higher density, CO₂ molecules mix with other gases due to the energy imparted by the Sun's heat. This mixing occurs due to molecular collisions, and although other factors like air currents play a role, diffusion is the primary reason CO₂ can reach higher altitudes than its density would suggest.

Furthermore, when a wine bottle is opened or moved from a cool environment to a warmer one, the gases inside the bottle mix with the surrounding atmosphere. Similarly, CO₂ in the Earth's atmosphere becomes part of the global atmospheric mix, even at higher altitudes. While CO₂ may have a higher density, its molecular behaviour and diffusion prevent it from forming isolated layers in the upper atmosphere. This mixing process is driven by the constant movement and kinetic energy of gas molecules, ensuring that CO₂ is distributed throughout the atmosphere.

In summary, despite its higher density, carbon dioxide's behaviour as a gas in the Earth's atmosphere is influenced by factors such as kinetic energy, molecular collisions, and diffusion. These properties prevent the formation of separate layers and allow CO₂ to mix with other gases at higher altitudes, contributing to the composition of the atmosphere.

Q199:

Graphite is a highly efficient electrical conductor. Why?

A199:

Graphite is a solid form of carbon found in the earth's crust. It is a naturally formed mineral that can be found in rocks that are igneous or metamorphic. Diamond and graphite are both minerals that are made of carbon, but they have different chemical patterns.

Graphite is a unique element because it combines metal and non-metal characteristics.

Because its electrons aren't restricted to a single location, graphite is an excellent conductor of electricity. Each carbon atom in graphite makes a covalent link with three other carbon atoms, and as a result, each carbon atom has one unpaired electron that becomes delocalized and is responsible for the material's electrical conductivity.

Unlike any other element, graphite possesses both metallic and non-metallic characteristics. It is a type of carbon that forms in the earth's crust under high temperatures and pressures. The process typically takes place at pressures of 75,000 pounds per square inch or higher.

The electric current flows through an element because electrons can move across it. This is the most important thing that makes an element electrically conductive. Electricity can flow through elements whose electrons aren't stuck in one place. The type of conductor relies on how easy it is for electrons to move through.

Q200:  

Diamonds are renowned for their remarkable hardness, a quality that distinguishes them and contributes to their widespread popularity. It's often said that a true diamond can even cut through glass. But what exactly makes diamonds so incredibly hard?

A200:

The exceptional hardness of diamonds is attributed to their unique composition and structure. These precious gems are formed deep within the Earth's mantle under conditions of extremely high temperature and pressure. Over billions of years (1–3.3 billion years for diamonds), carbon undergoes a transformation at depths ranging from 87 to 120 miles within the Earth's core. This process occurs under the influence of intense heat and pressure. As a result, the carbon atoms in diamonds rearrange themselves through a phenomenon known as covalent bonding. This rearrangement leads to the creation of a crystal lattice, where carbon atoms are arranged closely together, and they no longer interact with each other in the same way as in other forms of carbon.

The close arrangement of carbon atoms within this crystal lattice imparts an extraordinary level of strength and rigidity to diamonds. This unique atomic structure is what gives diamonds their exceptional hardness. This atomic arrangement is the reason why diamonds can resist scratching and maintain their pristine appearance even in challenging environments.

To quantify the scratch resistance of different minerals, the Mohs scale was developed by German geologist and mineralogist Friedrich Mohs in 1812. This scale assesses the ability of a material to scratch or be scratched by other materials. On the Mohs scale, diamonds achieve a perfect score of 10 out of 10, highlighting their unparalleled hardness. This places diamonds at the top of the hardness scale and underscores their ability to endure abrasion and retain their exquisite brilliance over time.

In conclusion, the exceptional hardness of diamonds stems from their distinct atomic structure that arises due to covalent bonding under conditions of high temperature and pressure. This unique arrangement of carbon atoms imparts an unmatched resistance to scratching, making diamonds one of the hardest naturally occurring substances in existence.

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