# Magnesium ribbon is added to dilute hydrochloric acid. Explain the changes in oxidation state that occur during this reaction, identifying which species is oxidised and which is reduced. Include in your answer what is meant by the terms oxidation and reduction in terms of electron transfer.

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

> When magnesium ribbon is placed into dilute hydrochloric acid, the ribbon dissolves and bubbles of gas are produced. The overall equation for the reaction is: Mg + 2HCl → MgCl₂ + H₂

## Mark scheme (5 marks)

1. Oxidation is the loss of electrons (by an atom or ion)
2. Reduction is the gain of electrons (by an atom or ion)
3. Magnesium is oxidised because it loses electrons / goes from oxidation state 0 to +2
4. Hydrogen ions (H⁺) are reduced because they gain electrons / go from oxidation state +1 to 0
5. This reaction is a redox reaction because oxidation and reduction occur simultaneously

## Key terms

- [oxidation](https://www.gradenine.co.uk/glossary/oxidation)
- [reduction](https://www.gradenine.co.uk/glossary/reduction)
- [oxidation state](https://www.gradenine.co.uk/glossary/oxidation-state)
- [electron transfer](https://www.gradenine.co.uk/glossary/electron-transfer)

## 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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