Question

Electrolysis is carried out in three cells:

• A. 1.0MCuSO₄ with Pt electrodes
• B. 1.0MCuSO₄ with Cu electrodes
• C. 1.0MKCl with Pt electrodes. If volume of electrolytic solution is maintained constant in each of the cell, which is correct set of pH changes in (A), (B) and (C) cell respectively?
• D. decrease in all the three

Hint:

pH changes depend on whether H⁺ or OH⁻ ions are produced at electrodes.

Answer 1

The Correct Option is C

Cell (A): Pt electrodes in CuSO₄. Cathode: Cu²++2e⁻ → Cu Anode: 2H₂O → O₂ + 4H⁺ + 4e⁻ ⟹ H⁺ increases, pH decreases. Cell (B): Cu electrodes in CuSO₄. Cathode: Cu²++2e⁻ → Cu Anode: Cu → Cu²++2e⁻ ⟹ No change in H⁺, pH constant. Cell (C): Pt electrodes in KCl. Cathode: 2H₂O+2e⁻ → H₂+2OH⁻ Anode: 2Cl⁻ → Cl₂+2e⁻ ⟹ OH⁻ increases, pH increases.