Explain what happens at each electrode when aqueous copper sulfate solution is electrolysed using copper electrodes. Include the names of the processes occurring at each electrode in your answer.

Edexcel GCSE Chemistry (1CH0) — 3.2 Electrolytic processes · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Electrolysis is used in industry to purify copper. Aqueous copper sulfate solution is used as the electrolyte, with copper used for both electrodes.

Model answer (4 marks)

At the cathode, Cu²⁺ ions gain electrons (reduction) and are deposited as copper metal:
Cu²⁺ + 2e⁻ → Cu(s)

At the anode, copper metal loses electrons (oxidation) and dissolves into the solution as Cu²⁺ ions:
Cu(s) → Cu²⁺ + 2e⁻

Examiner tips

  • Use the correct half‑reactions and state the process (reduction/oxidation) at each electrode
  • Show the electron transfer explicitly
  • Mention that the anode dissolves and the cathode deposits copper

Common mistakes

  • Confusing the direction of electron flow or the species reduced/oxidised
  • Writing the wrong half‑reaction for the anode
  • Omitting the fact that the anode loses mass

Mark scheme (4 marks)

  1. At the cathode, copper ions gain electrons (reduction occurs)
  2. Copper is deposited / forms at the cathode
  3. At the anode, copper atoms lose electrons (oxidation occurs)
  4. The anode dissolves / loses mass as copper atoms enter the solution as copper ions

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