# A student investigates the reactions of aqueous ammonium ions and aqueous carbonate ions with various reagents. Describe the observations the student would make when: (i) aqueous sodium hydroxide is added to an ammonium salt solution and the mixture is warmed, and (ii) dilute hydrochloric acid is added to an aqueous solution containing carbonate ions. Include the name of any gas produced in each case.

> AQA A-Level Chemistry (7405) — 3.2.6 Reactions of ions in aqueous solution (A-Level only) · Describe · 5 marks

## Mark scheme (5 marks)

1. (i) A pungent / sharp smell is produced on warming
2. (i) The gas produced is ammonia
3. (i) Damp red litmus paper turns blue (accept: damp universal indicator paper turns blue/purple)
4. (ii) Effervescence / bubbles are observed
5. (ii) The gas produced is carbon dioxide (accept: CO₂; accept: turns limewater milky as the test)

## Key terms

- [ammonium ions](https://www.gradenine.co.uk/glossary/ammonium-ions)
- [carbonate ions](https://www.gradenine.co.uk/glossary/carbonate-ions)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-investigates-the-reactions-of-e3c48f8a) · Published by Druglandscape Ltd.