# A reversible reaction is carried out in a closed container. The reaction reaches equilibrium. Explain what the term 'reversible reaction' means and describe the conditions needed for equilibrium to be reached.

> AQA GCSE Chemistry (8462) — 4.6.2 Reversible reactions and dynamic equilibrium · Explain · 4 marks

> Ammonium chloride decomposes when heated to form ammonia and hydrogen chloride. When cooled, ammonia and hydrogen chloride react to re-form ammonium chloride.

## Mark scheme (4 marks)

1. A reversible reaction is one where the products can react together to re-form the original reactants
2. The reaction must occur in a closed/sealed container (so neither reactants nor products can escape)
3. Equilibrium is reached when the forward reaction and the reverse reaction occur at the same rate
4. The concentrations of reactants and products remain constant at equilibrium

## Key terms

- [reversible reaction](https://www.gradenine.co.uk/glossary/reversible-reaction)
- [equilibrium](https://www.gradenine.co.uk/glossary/equilibrium)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-reversible-reaction-is-carried-out-6523cefe) · Published by Druglandscape Ltd.