Iron can be extracted from iron oxide by heating it with carbon. In this reaction, the iron oxide loses oxygen and the carbon gains oxygen. Explain what has been oxidised and what has been reduced in this reaction, and describe what the terms oxidation and reduction mean in terms of oxygen transfer.

WJEC A-Level Chemistry (Wales) — 1.8 Redox · Explain · 5 marks · View as Markdown

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

Iron oxide (Fe₂O₃) is heated with carbon (C). Iron metal and carbon dioxide are produced.

Model answer (5 marks)

Oxidation is the gain of oxygen.
Reduction is the loss of oxygen.
Carbon is oxidised because it gains oxygen to form CO₂.
Iron oxide is reduced because it loses oxygen to form Fe.
Oxidation and reduction occur simultaneously – this is a redox reaction.

Examiner tips

  • Use the terms ‘oxidation’ and ‘reduction’ exactly as defined in the scheme.
  • Show that carbon gains O and iron oxide loses O – this demonstrates the transfer of oxygen.
  • Mention that the two processes happen at the same time to justify the reaction is redox.

Common mistakes

  • Confusing ‘oxidised’ with ‘reduced’ – e.g. saying iron is oxidised. Failing to state that iron oxide loses oxygen. Using vague language such as ‘carbon reacts’ without specifying oxygen transfer.

Mark scheme (5 marks)

  1. Oxidation is the gain of oxygen
  2. Reduction is the loss of oxygen
  3. Carbon is oxidised because it gains oxygen (forming carbon dioxide)
  4. Iron oxide is reduced because it loses oxygen (to form iron)
  5. Oxidation and reduction occur simultaneously / this is a redox reaction

Key terms in this question

oxidation · reduction

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