# A technician in a hospital laboratory analyses a sample of a patient's urine. The technician suspects the sample contains ammonium ions, iron(II) ions and chloride ions. Describe the tests the technician should carry out to confirm the presence of each of these three ions, and state the expected result for each test.

> Edexcel A-Level Chemistry (9CH0) — 4.3 Qualitative analysis of ions · Describe · 5 marks

> Qualitative analysis of ions can be used to identify the cations and anions present in an unknown sample. Different reagents are used to produce characteristic observations that confirm the identity of specific ions.

## Mark scheme (5 marks)

1. Add sodium hydroxide solution to the sample and warm gently — ammonia gas is produced, which turns damp red litmus paper blue, confirming ammonium ions
2. Add sodium hydroxide solution to the sample — a green precipitate forms, confirming iron(II) ions
3. Acidify the sample with dilute nitric acid and add silver nitrate solution — a white precipitate forms, confirming chloride ions

## Key terms

- [ammonium ions](https://www.gradenine.co.uk/glossary/ammonium-ions)
- [iron(II) ions](https://www.gradenine.co.uk/glossary/iron-ii-ions)
- [chloride ions](https://www.gradenine.co.uk/glossary/chloride-ions)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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-technician-in-a-hospital-laboratory-d69f0ab7) · Published by Druglandscape Ltd.