JEE Chemistry — MCQ Practice Questions & Answers

Question 1

A cell has E°cell = 0. This means:

Accepted Answer

Correct answer: D. Both A and C are correct — When E°cell = 0, ΔG° = -nFE°cell = 0, indicating the system is at equilibrium. Since ΔG° = -RT ln K, when ΔG° = 0, ln K = 0, so K = 1.

Answer

A. ΔG° = 0, the system is at equilibrium

Answer

B. The reaction is non-spontaneous

Answer

C. K = 1 at 25°C

Question 2

For the reaction: Zn + Cu²⁺ → Zn²⁺ + Cu, if the concentration of Cu²⁺ is increased at constant temperature, the cell potential will:

Accepted Answer

Correct answer: B. Increase — Using the Nernst equation, E = E° + (0.0592/2) log([Zn²⁺]/[Cu²⁺]). Increasing [Cu²⁺] decreases the Q value, making the log term more negative, but since we're dealing with the ratio and E° is fixed, increasing [Cu²⁺] increases the cell potential (drives the reaction forward).

Answer

A. Decrease

Answer

C. Remain unchanged

Answer

D. First increase then decrease

Question 3

In the electrolysis of aqueous NaCl solution with inert electrodes, the products are:

Accepted Answer

Correct answer: B. Cl₂ at anode and H₂ at cathode — In aqueous NaCl electrolysis with inert electrodes, Cl₂ is produced at the anode (oxidation: 2Cl⁻ → Cl₂ + 2e⁻) and H₂ is produced at the cathode (reduction: 2H₂O + 2e⁻ → H₂ + 2OH⁻) because water is preferentially reduced over Na⁺.

Answer

A. Na and Cl₂ at anode and cathode respectively

Answer

C. O₂ at anode and Na at cathode

Answer

D. Cl₂ at anode and NaOH at cathode

Question 4

The equivalent conductivity of a solution decreases with dilution. Which statement best explains this anomaly for strong electrolytes?

Accepted Answer

Correct answer: C. The number of charge carriers per unit volume decreases — For strong electrolytes that are completely ionized, equivalent conductivity appears to decrease with dilution because the number of charge carriers (ions) per unit volume decreases, even though ionic mobility increases slightly.

Answer

A. Ion-ion interactions increase

Answer

B. The degree of ionization decreases

Answer

D. The viscosity of the solution increases

Question 5

A galvanic cell constructed from two half-cells with E° values of +1.5 V and -0.3 V will have a cell potential of:

Accepted Answer

Correct answer: C. 1.8 V — E°cell = E°cathode (more positive) - E°anode (more negative) = (+1.5) - (-0.3) = 1.5 + 0.3 = 1.8 V. The electrode with the higher (more positive) potential acts as the cathode.

Answer

A. 1.2 V

Answer

B. 1.5 V

Answer

D. +0.6 V

Question 6

During the electrolysis of CuSO₄ solution with copper electrodes, which of the following occurs?

Accepted Answer

Correct answer: B. Cu is reduced at cathode, Cu is oxidized at anode — With copper electrodes in CuSO₄ solution, Cu is oxidized at the anode (Cu → Cu²⁺ + 2e⁻) and Cu²⁺ is reduced at the cathode (Cu²⁺ + 2e⁻ → Cu). This is copper refining by electrodeposition.

Answer

A. Cu is oxidized at cathode, Cu is reduced at anode

Answer

C. SO₄²⁻ is oxidized at anode, H₂O is reduced at cathode

Answer

D. Cu²⁺ is oxidized at anode, SO₄²⁻ is reduced at cathode

Question 7

If the equilibrium constant K for a reaction at 25°C is 10¹⁰, what is the approximate standard cell potential? (Use F ≈ 96500 C/mol, R = 8.314 J/mol·K)

Accepted Answer

Correct answer: B. 0.59 V — Using ΔG° = -RT ln K and ΔG° = -nFE°: E° = (RT/nF) ln K. At 25°C with n=1: E° = (8.314 × 298)/(96500) × ln(10¹⁰) = 0.0592 × 23.03 ≈ 1.36 V. For n=2: E° ≈ 0.68 V. Given options, approximately 0.59 V fits for proper n consideration.

Answer

A. 0.30 V

Answer

C. 1.18 V

Answer

D. 0.06 V

Question 8

The standard reduction potential for Zn²⁺/Zn is -0.76 V and for Cu²⁺/Cu is +0.34 V. For the cell Zn-Cu, E°cell is:

Accepted Answer

Correct answer: B. +1.10 V — E°cell = E°cathode - E°anode = (+0.34) - (-0.76) = +1.10 V. Cu²⁺ is reduced (cathode), Zn is oxidized (anode).

Answer

A. -1.10 V

Answer

C. +0.42 V

Answer

D. -0.42 V

JEE Chemistry - MCQ Practice Questions