Cathode reduction in aqueous CuSO₄ electrolysis

Steps:

• Cathode involves reduction of cations or water.
• Possible reactions: Cu²⁺ to Cu or H₂O to H₂/OH⁻.
• Cu²⁺ has higher standard reduction potential (+0.34 V) than H⁺/H₂ (0 V).
• Thus, Cu²⁺ discharges preferentially: Cu²⁺ + 2e⁻ → Cu.

Why A is correct:

• Cu²⁺ ions reduce to Cu metal as copper's electrode potential exceeds that of hydrogen, per electrochemical series rules.

Why the others are wrong:

• B: Applies to cations harder to reduce than H⁺ (e.g., Na⁺), not Cu²⁺.
• C: Oxidation reaction for anode oxygen evolution, not cathode reduction; O²⁻ absent in solution.
• D: SO₄²⁻ not reduced at cathode; equation violates standard electrochemistry.

Final answer: A