# Iron rusting is an example of an oxidation reaction. A student investigates the reaction between iron(III) oxide and carbon monoxide to produce iron and carbon dioxide. Explain why this reaction is a redox reaction, identifying which substance is oxidised and which is reduced.

> OCR A-Level Chemistry A (H432) — 2.3 Acid-base and redox reactions · Explain · 5 marks

> Iron(III) oxide reacts with carbon monoxide as shown: Fe₂O₃ + 3CO → 2Fe + 3CO₂

## Mark scheme (5 marks)

1. Oxidation is the gain of oxygen / carbon monoxide gains oxygen
2. Carbon monoxide (CO) is oxidised
3. Reduction is the loss of oxygen / iron(III) oxide loses oxygen
4. Iron(III) oxide (Fe₂O₃) is reduced
5. Both oxidation and reduction occur simultaneously / at the same time, making it a redox reaction

## Key terms

- [oxidation](https://www.gradenine.co.uk/glossary/oxidation)
- [redox reaction](https://www.gradenine.co.uk/glossary/redox-reaction)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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