Chemistry Paper-II
(English Version)
Time: 3 Hours | Max. Marks: 60
SECTION – A
Answer ALL the questions. (10 × 2 = 20 M)
1. What are isotonic solutions?
Isotonic solutions are solutions that have the same osmotic pressure. When two solutions are isotonic, the rate of osmosis is equal in both directions, and there is no net movement of solvent molecules. Example: A 0.9% NaCl solution and blood plasma are isotonic to each other.
2. What are pseudo first order reactions? Give one example?
Pseudo first-order reactions are reactions that appear to be first-order, but in reality, they are not. This occurs when one reactant is present in large excess, making its concentration essentially constant. Example: The hydrolysis of ester in water, where water is in excess and the reaction behaves like a first-order reaction.
3. Give composition of the following alloys:
a) Bronze – Bronze is an alloy of copper and tin, with copper typically making up 88-95% of the alloy and tin around 5-12%.
b) German silver – German silver is an alloy of copper, zinc, and nickel. It typically contains 60% copper, 20% zinc, and 20% nickel.
b) German silver – German silver is an alloy of copper, zinc, and nickel. It typically contains 60% copper, 20% zinc, and 20% nickel.
4. What is tailing of mercury? How is it removed?
Tailing of mercury refers to the formation of a thin layer of mercury on the surface of a container or apparatus. It can be removed by using a solvent such as nitric acid or by heating the apparatus, which evaporates the mercury.
5. How is XeO3 prepared? Explain the structure of XeO3?
Xenon trioxide (XeO3) can be prepared by reacting xenon tetroxide (XeO4) with hydrogen. Its structure is a pyramidal shape, where the xenon atom is at the center bonded to three oxygen atoms, with one lone pair on the xenon atom.
6. Calculate the spin-only magnetic moment?
The spin-only magnetic moment (μ) is calculated using the formula:
μ = √[n(n+2)] μB
Where n is the number of unpaired electrons and μB is the Bohr magneton. If n = 2, then:
μ = √[2(2+2)] = √8 = 2.83 μB
μ = √[n(n+2)] μB
Where n is the number of unpaired electrons and μB is the Bohr magneton. If n = 2, then:
μ = √[2(2+2)] = √8 = 2.83 μB
7. What is tincture of iodine? What is its use?
Tincture of iodine is an alcoholic solution of iodine (about 2-7% iodine in alcohol). It is used as an antiseptic to clean wounds and prevent infections.
8. What are antacids? Give examples?
Antacids are substances that neutralize stomach acid and relieve indigestion or heartburn. Examples include sodium bicarbonate, magnesium hydroxide, and calcium carbonate.
9. What is the stereochemical result of SN1 and SN2 reactions?
In SN1 reactions, the reaction occurs in two steps: formation of a carbocation intermediate and substitution by a nucleophile. The stereochemistry is racemized because of the planar nature of the carbocation.
In SN2 reactions, the nucleophile attacks the electrophile from the opposite side, leading to inversion of configuration at the carbon atom.
In SN2 reactions, the nucleophile attacks the electrophile from the opposite side, leading to inversion of configuration at the carbon atom.
10. Write equations showing the conversion of:
i) Acetic acid to Acetyl chloride:
CH₃COOH + SOCl₂ → CH₃COCl + SO₂ + HCl
ii) Benzoic acid to Benzamide:
C₆H₅COOH + NH₃ → C₆H₅CONH₂ + H₂O
CH₃COOH + SOCl₂ → CH₃COCl + SO₂ + HCl
ii) Benzoic acid to Benzamide:
C₆H₅COOH + NH₃ → C₆H₅CONH₂ + H₂O
SECTION – B
Answer any SIX of the following questions. (6 × 4 = 24 M)
11. Derive Bragg’s equation.
Bragg’s law relates the angle of diffraction to the wavelength of the X-rays and the spacing between crystal planes. The equation is given as:
nλ = 2d sinθ
Where n is the order of diffraction, λ is the wavelength of the X-rays, d is the distance between crystal planes, and θ is the angle of diffraction.
nλ = 2d sinθ
Where n is the order of diffraction, λ is the wavelength of the X-rays, d is the distance between crystal planes, and θ is the angle of diffraction.
12. State Raoult’s law. Vapour pressure of water at 293K is 17.535 mm Hg. Calculate the vapour pressure of the solution at 293K when 25 g of glucose is dissolved in 450 g of water.
Raoult’s law states that the partial vapor pressure of a solvent in a solution is proportional to the mole fraction of the solvent.
Pₛₒᵤₗᵤₜᵢₒₙ = Xₛₒᵤₗᵤₜᵢₒₙ * Pₛₒᵤₗᵤₜ (pure)
First, calculate the mole fraction of the solvent (water):
Moles of glucose = 25/180 = 0.1389 mol
Moles of water = 450/18 = 25 mol
Mole fraction of water: Xₓ = 25/(25 + 0.1389) = 0.9945
Now, calculate the vapor pressure of the solution: Pₛₒᵤₗᵤₜᵢₒₙ = 0.9945 * 17.535 mm Hg = 17.46 mm Hg
First, calculate the mole fraction of the solvent (water):
Moles of glucose = 25/180 = 0.1389 mol
Moles of water = 450/18 = 25 mol
Mole fraction of water: Xₓ = 25/(25 + 0.1389) = 0.9945
Now, calculate the vapor pressure of the solution: Pₛₒᵤₗᵤₜᵢₒₙ = 0.9945 * 17.535 mm Hg = 17.46 mm Hg
13. Explain the purification of sulphide ore by froth flotation method?
In froth flotation, the crushed ore is mixed with water and certain chemicals that make the metal sulfide particles hydrophobic (water-repellent). Air is bubbled through the mixture, and the hydrophobic ore particles attach to the bubbles, rising to the surface. The waste material (gangue) remains in the water and is removed, leaving behind the purified ore.
14. What is catalysis? How is catalysis classified? Give two examples for each type of catalysis?
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance (catalyst) that is not consumed in the reaction.
Homogeneous catalysis occurs when the catalyst and reactants are in the same phase. Example: Acid catalysis in esterification.
Heterogeneous catalysis occurs when the catalyst is in a different phase from the reactants. Example: Catalytic converters in cars (solid catalyst and gaseous reactants).
Homogeneous catalysis occurs when the catalyst and reactants are in the same phase. Example: Acid catalysis in esterification.
Heterogeneous catalysis occurs when the catalyst is in a different phase from the reactants. Example: Catalytic converters in cars (solid catalyst and gaseous reactants).
15. Explain Werner’s theory of coordination compounds with suitable examples.
Werner’s theory states that coordination compounds have a central metal atom or ion bonded to a set of ligands. The metal atom has a certain number of coordinate bonds, and the ligands are arranged around the metal ion in a particular geometry. Example: In [Co(NH₃)₆]³⁺, cobalt is the central metal ion, and ammonia molecules are the ligands.
16. Give the sources of the following vitamins and name the disease caused by their deficiency:
a) A – Found in liver, carrots, and green leafy vegetables. Deficiency causes night blindness.
b) D – Found in fish, eggs, and sunlight. Deficiency causes rickets.
c) E – Found in vegetable oils, nuts, and seeds. Deficiency causes reproductive problems.
d) K – Found in leafy vegetables, fish, and meat. Deficiency causes excessive bleeding.
b) D – Found in fish, eggs, and sunlight. Deficiency causes rickets.
c) E – Found in vegetable oils, nuts, and seeds. Deficiency causes reproductive problems.
d) K – Found in leafy vegetables, fish, and meat. Deficiency causes excessive bleeding.
17. Write the name and structures of the monomers of the following polymers.
a) Teflon – Monomer: Tetrafluoroethylene (TFE) Structure: C₂F₄
b) Bakelite – Monomer: Phenol and formaldehyde Structure: C₆H₅OH + CH₂O
c) PVC – Monomer: Vinyl chloride Structure: C₂H₃Cl
d) Buna-N – Monomer: Butadiene and acrylonitrile Structure: C₄H₆ + C₃H₃N
b) Bakelite – Monomer: Phenol and formaldehyde Structure: C₆H₅OH + CH₂O
c) PVC – Monomer: Vinyl chloride Structure: C₂H₃Cl
d) Buna-N – Monomer: Butadiene and acrylonitrile Structure: C₄H₆ + C₃H₃N
18. Write short notes on:
i) Carbylamine reaction – In the carbylamine reaction, primary amines react with chloroform (CHCl₃) in the presence of alkali to form isocyanides (carbylamines). Example: RNH₂ + CHCl₃ + KOH → RCN + KCl + H₂O
ii) Sandmeyer reaction – The Sandmeyer reaction is a method for the synthesis of aryl halides from aryl diazonium salts using copper salts. Example: ArN₂⁺ + CuX → ArX + Cu₂X₂
ii) Sandmeyer reaction – The Sandmeyer reaction is a method for the synthesis of aryl halides from aryl diazonium salts using copper salts. Example: ArN₂⁺ + CuX → ArX + Cu₂X₂
SECTION – C
Answer any TWO of the following questions. (2 × 8 = 16 M)
19. a) Give a detailed account of the collision theory of reaction rates of bimolecular gaseous reactions.
The collision theory suggests that molecules must collide with sufficient energy and proper orientation for a chemical reaction to occur. The rate of reaction is proportional to the number of effective collisions. For bimolecular reactions, the rate is also proportional to the concentration of the two reactants. The activation energy (Ea) is the minimum energy required for a reaction to occur, and the frequency factor (A) represents the frequency of collisions that lead to a reaction.
20. a) Discuss the redox reaction involved in the corrosion of iron.
The corrosion of iron involves both oxidation and reduction reactions:
Oxidation: Fe → Fe²⁺ + 2e⁻ (Iron loses electrons)
Reduction: O₂ + 4e⁻ + 2H₂O → 4OH⁻ (Oxygen gains electrons)
The iron reacts with oxygen and water in the presence of atmospheric moisture, forming rust (hydrated iron oxide). The corrosion process is accelerated by the presence of salt and acids in the environment.
Oxidation: Fe → Fe²⁺ + 2e⁻ (Iron loses electrons)
Reduction: O₂ + 4e⁻ + 2H₂O → 4OH⁻ (Oxygen gains electrons)
The iron reacts with oxygen and water in the presence of atmospheric moisture, forming rust (hydrated iron oxide). The corrosion process is accelerated by the presence of salt and acids in the environment.
21. a) Discuss the method of preparation and properties of sulphur dioxide.
Sulfur dioxide (SO₂) can be prepared by burning sulfur in excess oxygen or by heating metal sulfides (e.g., zinc sulfide) with oxygen:
S + O₂ → SO₂
SO₂ is a colorless, toxic gas with a pungent odor. It dissolves in water to form sulfurous acid (H₂SO₃) and is an important intermediate in the industrial production of sulfuric acid.
S + O₂ → SO₂
SO₂ is a colorless, toxic gas with a pungent odor. It dissolves in water to form sulfurous acid (H₂SO₃) and is an important intermediate in the industrial production of sulfuric acid.