Electrochemistry — Chemistry STD 12 Science — Question

• It is used to measure relative strengths of various oxidants and reductants.
• It is used to calculate standard cell potential.
• It is used to predict possible reactions.

I₂ + 2e^- → 2I^- ; Eº = 0.54 V

Cl₂ + 2e^- → 2Cl^- ; Eº = 1.36 V

Mn³⁺ +e^- → Mn²⁺ ; Eº = 1.50 V

Fe³⁺ + e^- → Fe²⁺ ; Eº = 0.77 V

O₂ + 4H⁺ + 4e^- → 2H₂O ; Eº = 1.23 V

1. Which of the following statements is correct?

1. Cl^- is oxidised by O₂.
2. Fe²⁺ is oxidised by iodine.
3. I^- is oxidised by chlorine.
4. Mn²⁺ is oxidised by chlorine.

2. Mn³⁺ is not stable in acidic medium, while Fe³⁺ is stable because:

1. O₂ oxidises Mn²⁺ to Mn³⁺
2. O₂ oxidises both Mn²⁺ to Mn³⁺ and Fe²⁺ to Fe³⁺
3. Fe³⁺ oxidises H₂O to O₂
4. Mn³⁺ oxidises H₂O to O₂

3. The strongest reducing agent in the aqueous solution is:

1. I^-
2. Cl^-
3. Mn²⁺
4. Fe²⁺

4. The emf for the following reaction is:

$\text{I}_2+\text{KCl}\rightleftharpoons2\text{KI}+\text{Cl}_2$

1. -0.82 V
2. +0.82 V
3. -0.73 V
4. +0.73 V

5. Which of the following statements is correct for the following reaction?

Fe³⁺ + Mn²⁺ → Fe²⁺ + Mn³⁺

1. The emf of the cell is positive.
2. Fe³⁺ oxidises Mn²⁺.
3. The reaction does not occur.
4. All are correct.