Anode mass decreases linearly due to constant dissolution rate

Steps:

• Anode reaction: Cu(s) → Cu²⁺(aq) + 2e⁻, dissolving copper and reducing anode mass.
• Cathode reaction: Cu²⁺(aq) + 2e⁻ → Cu(s), depositing copper but irrelevant for anode weighing.
• Constant current means constant electron flow, so constant rate of Cu atoms lost from anode.
• Plot of anode mass vs. time is linear decrease, as mass loss ∝ current × time (Faraday's first law).

Why C is correct:

• C shows straight-line decrease, matching constant mass loss rate from Faraday's laws of electrolysis.

Why the others are wrong:

• A: Shows increase, but anode dissolves, so mass decreases.
• B: Shows curved decrease, but constant current yields linear, not accelerating, loss.
• D: Shows no change or irregular, but steady electrolysis causes consistent mass reduction.

Final answer: C