Iron can be extracted from iron(III) oxide by reaction with carbon monoxide. The equation for this reaction is: Fe₂O₃ + 3CO → 2Fe + 3CO₂. Explain what happens to iron and carbon monoxide in terms of oxidation and reduction during this reaction.

Edexcel A-Level Chemistry (9CH0) — 3.1 Oxidation and reduction · Explain · 5 marks · View as Markdown

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

Iron ore contains iron(III) oxide, Fe₂O₃. In industry, carbon monoxide is used to extract iron from its ore.

Model answer (5 marks)

Iron(III) oxide loses oxygen atoms, so iron(III) oxide is reduced.
Carbon monoxide gains oxygen atoms to form carbon dioxide, so carbon monoxide is oxidised.
Thus iron(III) oxide is reduced while carbon monoxide is oxidised, making this a redox reaction.

Examiner tips

  • Use the term ‘reduced’ for iron(III) oxide and ‘oxidised’ for CO. Mention the loss of oxygen from Fe₂O₃ and the gain of oxygen by CO. Show the simultaneous oxidation and reduction to justify the redox nature.

Common mistakes

  • Saying iron is oxidised or CO is reduced – the opposite is true. Forgetting to state that oxygen is removed from Fe₂O₃. Using vague wording such as ‘iron changes’ without specifying oxidation state.

Mark scheme (5 marks)

  1. Iron(III) oxide loses oxygen / iron gains no oxygen / oxygen is removed from iron(III) oxide
  2. Iron(III) oxide is reduced (because it loses oxygen)
  3. Carbon monoxide gains oxygen to form carbon dioxide
  4. Carbon monoxide is oxidised (because it gains oxygen)
  5. This reaction is a redox reaction because oxidation and reduction happen simultaneously / one substance is oxidised whilst the other is reduced

Key terms in this question

oxidation · reduction

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