Question

Electrolysis is carried out in three cells: (A) 1.0M CuSO₄ using Pt electrodes (B) 1.0M CuSO₄ using Cu electrodes (C) 1.0M KCl using Pt electrodes If volume of electrolyte solution is maintained constant in each cell, which is the correct set of change of pH in the (A), (B) and (C) cell respectively?

• A. decrease in all the three
• B. increase in all the three
• C. decrease, constant, increase
• D. increase, constant, increase

Hint:

In electrolysis, pH change depends on whether H⁺ or OH⁻ ions are produced.

Answer 1

The Correct Option is C

Step 1: Cell (A): Pt electrodes in CuSO₄ Anode reaction produces H⁺ ions ⟹ pH decreases.
Step 2: Cell (B): Cu electrodes in CuSO₄ Copper dissolves at anode and deposits at cathode ⟹ no net change in H⁺ ⟹ pH constant.
Step 3: Cell (C): Pt electrodes in KCl Cathode produces OH⁻ ions ⟹ pH increases.