Copper(II) sulfate solution is electrolysed using inert electrodes. State what is observed at each electrode and identify the ion that is discharged at each electrode.

Pearson Edexcel International GCSE Chemistry (4CH1) — 1.9 Electrolysis · State · 4 marks · View as Markdown

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

Copper(II) sulfate solution contains copper(II) ions (Cu²⁺), sulfate ions (SO₄²⁻), hydrogen ions (H⁺), and hydroxide ions (OH⁻). Inert electrodes are used throughout the electrolysis.

Model answer (4 marks)

At the cathode a pink/orange‑red solid is deposited – copper metal.
The discharged ion is Cu²⁺.
At the anode bubbles of gas are produced – oxygen gas.
The discharged ion is OH⁻.

Examiner tips

  • Use the exact colour description (pink/orange‑red) and state the product (copper metal).
  • Mention the ion discharged at each electrode – Cu²⁺ at cathode, OH⁻ at anode.

Mark scheme (4 marks)

  1. At the cathode: a pink/orange-red solid is deposited (copper metal forms)
  2. At the cathode: copper(II) ions / Cu²⁺ ions are discharged
  3. At the anode: bubbles of gas are produced (oxygen gas is given off)
  4. At the anode: hydroxide ions / OH⁻ ions are discharged

Key terms in this question

inert · ion · discharged

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