Science (086) — AI-generated practice question

At the Anode (impure copper): The impure copper dissolves into the electrolyte (acidified copper sulphate solution). Copper atoms lose electrons and go into solution as Cu²⁺ ions.

At the Cathode (pure copper strip): Cu²⁺ ions from the electrolyte gain electrons and get deposited as pure copper.

Why insoluble impurities don't deposit on cathode: The impurities present in impure copper (anode) that are insoluble do not dissolve into the electrolyte. They simply fall to the bottom of the anode and collect as anode mud. Since they never enter the solution as ions, they cannot be deposited at the cathode. Only copper ions migrate and deposit on the cathode.

Source: Chapter 3, Section 3.4.6 – Refining of Metals

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• Examiners expect you to clearly name both electrodes and state what happens at each — dissolution at anode, deposition at cathode.
• The key point for the second part is the word "insoluble" — impurities that don't dissolve can't form ions, so they can't migrate to the cathode. They settle as anode mud (this term is expected).
• Avoid vague statements like "they are heavy" — the correct reason is they don't dissolve into the electrolyte.