# Describe the characteristic reactions of a base with an acid and with ammonium salts, stating what is observed in each reaction.

> Cambridge International IGCSE Chemistry (0620) — 7.1 The characteristic properties of acids and bases · Describe · 4 marks

## Mark scheme (4 marks)

1. A base reacts with an acid in a neutralisation reaction
2. Observation for acid–base reaction: the mixture warms up / temperature rises (exothermic)
3. A base reacts with an ammonium salt (when heated) to produce ammonia gas
4. Observation for base–ammonium salt reaction: ammonia has a pungent/choking smell and turns damp red litmus paper blue

## Key terms

- [base](https://www.gradenine.co.uk/glossary/base)
- [ammonium salt](https://www.gradenine.co.uk/glossary/ammonium-salt)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-characteristic-reactions-of-a-755a4221) · Published by Druglandscape Ltd.