Copper can be extracted from copper oxide by heating it with carbon. Explain why carbon can be used to extract copper from copper oxide, and why this method cannot be used to extract aluminium from aluminium oxide.

WJEC GCSE Chemistry (Wales) — 2.3 Metals and their extraction · Explain · 4 marks · View as Markdown

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

Metals differ in how reactive they are. This affects the methods that can be used to extract them from their ores.

Model answer (4 marks)

Carbon is more reactive than copper, so it can displace copper from copper oxide.
Carbon reduces CuO by removing oxygen, forming CO or CO₂ and leaving Cu.
Aluminium is more reactive than carbon, so carbon cannot displace aluminium from Al₂O₃.
Aluminium must be extracted by electrolysis because carbon cannot reduce Al₂O₃.

Examiner tips

  • Use the term ‘displace’ to show the redox idea. Show the reaction CuO + C → Cu + CO (or CO₂).
  • Mention that aluminium’s high reactivity means it forms a stable oxide that carbon cannot reduce.

Mark scheme (4 marks)

  1. Carbon is more reactive than copper (so carbon can displace copper from copper oxide)
  2. Carbon reduces copper oxide / removes oxygen from copper oxide
  3. Aluminium is more reactive than carbon (so carbon cannot displace aluminium)
  4. Aluminium must be extracted by electrolysis (because carbon cannot reduce aluminium oxide)

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