Chapters: Solutions • Electrochemistry • Chemical Kinetics
Maximum Marks: 30
Time: 1 Hour
General Instructions
- All questions are numerical/problem-based.
- Show the complete calculation and appropriate units.
- Use log 2 = 0.3010, log 3 = 0.4771 wherever required.
- Take F = 96500 C mol⁻¹ and R = 8.314 J K⁻¹ mol⁻¹, wherever required.
SECTION A — 1 × 6 = 6 Marks
Answer all questions.
Q1. Calculate the molality of a solution prepared by dissolving 18 g glucose (M = 180 g mol⁻¹) in 180 g of water.
Q2. The vapour pressure of pure water at 300 K is 31.8 mm Hg. Calculate the vapour pressure of a solution containing 1 mole of glucose in 9 moles of water.
Q3. Calculate the EMF of the cell at 298 K:
Zn | Zn²⁺ (0.1 M) || Cu²⁺ (0.01 M) | Cu
Given: E°cell = 1.10 V.
Q4. A current of 2 A is passed through a CuSO₄ solution for 30 minutes. Calculate the mass of copper deposited.
(Molar mass of Cu = 63.5 g mol⁻¹)
Q5. A first-order reaction has a half-life of 20 minutes. Calculate its rate constant.
Q6. For a reaction, the rate constant is 2.0 × 10⁻³ s⁻¹. Calculate its half-life.
SECTION B — 2 × 6 = 12 Marks
Answer all questions.
Q7. 5.85 g NaCl is dissolved in 500 g water. Calculate the depression in freezing point.
Given: Kf = 1.86 K kg mol⁻¹.
Assume complete dissociation of NaCl.
Q8. Calculate the molarity of a solution prepared by dissolving 4.9 g H₂SO₄ in water to make the final volume 250 mL.
(Molar mass of H₂SO₄ = 98 g mol⁻¹)
Q9. Calculate the standard Gibbs energy change for a cell reaction involving n = 2 electrons, if E°cell = 1.10 V.
Given: F = 96500 C mol⁻¹.
Q10. The conductivity of a 0.02 M KCl solution is 2.5 × 10⁻³ S cm⁻¹. Calculate its molar conductivity.
Q11. For a first-order reaction, 75% of the reactant decomposes in 40 minutes. Calculate the rate constant.
Q12. A reaction follows second-order kinetics. Its rate constant is 0.5 L mol⁻¹ s⁻¹ and initial concentration is 0.2 mol L⁻¹. Calculate the half-life of the reaction.
SECTION C — 3 × 4 = 12 Marks
Answer all questions.
Q13. A solution is prepared by dissolving 10 g of a non-volatile solute in 90 g of water. The vapour pressure of pure water at a certain temperature is 40 mm Hg, while that of the solution is 38 mm Hg.
Calculate the molar mass of the solute.
Q14. A conductivity cell containing 0.01 M KCl solution has a resistance of 100 Ω. The conductivity of the solution is 1.41 × 10⁻³ S cm⁻¹.
Calculate:
a) Cell constant
b) Conductance of the solution
c) Molar conductivity of KCl
Q15. A galvanic cell is represented as:
Mg | Mg²⁺ (0.01 M) || Cu²⁺ (0.001 M) | Cu
Given:
E°(Mg²⁺/Mg) = −2.37 V
E°(Cu²⁺/Cu) = +0.34 V
Calculate:
a) E°cell
b) Ecell at 298 K
c) ΔG° for the cell reaction
Q16. The decomposition of a substance follows first-order kinetics. Its concentration decreases from 0.80 M to 0.20 M in 30 minutes.
Calculate:
a) Rate constant
b) Half-life
c) Time required for the concentration to decrease from 0.20 M to 0.05 M
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