Electrolysis reactions in aqueous CuSO4 with inert carbon electrodes

Steps:

• At cathode (negative): Cu²⁺ ions reduced to Cu metal, depositing reddish-brown layer.
• At anode (positive): Water oxidized to O₂ gas, releasing H⁺ ions.
• Cu²⁺ ions deplete from solution as they're consumed at cathode.
• Blue color from Cu²⁺(aq) fades over time due to ion removal.

Why C is correct:

• Cu²⁺ ions are selectively discharged at cathode (E° = +0.34 V > H₂O/H₂), depleting blue [Cu(H₂O)₆]²⁺ complex per Faraday's laws.

Why the others are wrong:

• A: Anode produces O₂ bubbles, not pink solid (pink is Co²⁺, irrelevant here).
• B: Cathode deposits solid Cu, no H₂ bubbles (Cu²⁺ easier to reduce than H₂O).
• D: Inert carbon cathode unchanged; no dissolution occurs.

Final answer: C