A student carries out electrolysis of copper chloride solution using inert electrodes. Explain what happens at each electrode, including the names of the products formed.

OCR GCSE Chemistry A: Gateway Science (J248) — C3.4 Electrolysis · Explain · 4 marks · View as Markdown

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

Copper chloride solution contains copper ions (Cu²⁺) and chloride ions (Cl⁻) that are free to move through the electrolyte. When electricity is passed through the solution, chemical reactions occur at both electrodes.

Model answer (4 marks)

At the cathode (negative electrode) Cu²⁺ ions are attracted and are reduced:
Cu²⁺ + 2e⁻ → Cu(s). Copper metal is deposited on the electrode.

At the anode (positive electrode) Cl⁻ ions are attracted and are oxidised:
2Cl⁻ → Cl₂(g) + 2e⁻. Chlorine gas is evolved.

Examiner tips

Use the word ‘reduction’ for the cathode and ‘oxidation’ for the anode.
Show the ion movement (Cu²⁺ to cathode, Cl⁻ to anode).
Include the balanced half‑reactions and the products (Cu(s) and Cl₂(g)).

Common mistakes

Writing the wrong electrode for a reaction (e.g., copper deposited at the anode).
Forgetting to state that chlorine gas is produced at the anode.
Using the wrong half‑reaction (e.g., Cu⁺ instead of Cu²⁺).

Mark scheme (4 marks)

Copper ions (Cu²⁺) move to the cathode (negative electrode)
Copper is deposited at the cathode because the copper ions gain electrons / reduction occurs at the cathode
Chloride ions (Cl⁻) move to the anode (positive electrode)
Chlorine gas is produced at the anode because chloride ions lose electrons / oxidation occurs at the anode

Key terms in this question

inert