# Magnesium ribbon is placed into copper sulfate solution. The blue colour of the solution fades and a reddish-brown solid forms on the magnesium. Explain, in terms of electron transfer, why this reaction is described as a redox reaction. In your answer, identify which species is oxidised and which is reduced.

> AQA A-Level Chemistry (7405) — 3.1.7 Oxidation, reduction and redox equations · Explain · 5 marks

> Magnesium ribbon is placed into copper sulfate solution. The blue colour of the solution fades and a reddish-brown solid forms on the magnesium.

## Mark scheme (5 marks)

1. Magnesium atoms lose electrons
2. Magnesium is oxidised (because it loses electrons)
3. Copper ions gain electrons
4. Copper ions are reduced (because they gain electrons)
5. Both oxidation and reduction occur simultaneously, so the reaction is a redox reaction

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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