Reverse Connections for Cathode Plating

Steps:

• In electroplating, copper ions from CuSO4 solution reduce and deposit on the cathode.
• The steel key must be the cathode to attract Cu2+ ions for coating.
• If connections are reversed, the key acts as anode, oxidizing instead of plating.
• Reversing connections makes the key the cathode, enabling deposition.

Why D is correct:

• The cathode is the negative electrode where reduction occurs, per Faraday's laws of electrolysis, depositing Cu atoms on the key.

Why the others are wrong:

• A: Higher concentration increases plating rate but doesn't fix incorrect polarity.
• B: Dilute sulfuric acid lacks Cu2+ ions needed for copper plating.
• C: Identical to D, but listed separately; no unique correction.

Final answer: D