# A student has three unlabelled solutions: copper(II) sulfate, iron(III) chloride, and zinc sulfate. Describe how the student could use aqueous ammonia to distinguish between all three solutions. Include the observations that would confirm the identity of each solution.

> 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. Add excess aqueous ammonia to each solution (award for describing addition of aqueous ammonia to each solution)
2. Copper(II) sulfate: pale blue / light blue precipitate forms initially
3. Copper(II) sulfate: precipitate dissolves in excess ammonia to give a deep blue / dark blue solution
4. Iron(III) chloride: red-brown / orange-brown precipitate that does not dissolve in excess ammonia
5. Zinc sulfate: white precipitate that dissolves in excess ammonia to give a colourless solution

## Key terms

- [aqueous ammonia](https://www.gradenine.co.uk/glossary/aqueous-ammonia)
- [copper(II) sulfate](https://www.gradenine.co.uk/glossary/copper-ii-sulfate)
- [iron(III) chloride](https://www.gradenine.co.uk/glossary/iron-iii-chloride)
- [zinc sulfate](https://www.gradenine.co.uk/glossary/zinc-sulfate)

## 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-has-three-unlabelled-solutions-2a28fa82) · Published by Druglandscape Ltd.