# A geologist discovers a mineral sample and suspects it contains iron(III) ions, calcium ions and sulfate ions. Describe the tests the geologist would carry out to confirm the presence of each of these three ions, giving the expected observation for each test.

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

> The geologist dissolves the mineral sample in dilute hydrochloric acid to produce a solution for testing.

## Mark scheme (5 marks)

1. Add sodium hydroxide solution to test for iron(III) ions
2. Observation for iron(III) ions: a rust-brown / reddish-brown precipitate forms
3. Add dilute hydrochloric acid followed by barium chloride solution to test for sulfate ions
4. Observation for sulfate ions: a white precipitate forms
5. Add dilute hydrochloric acid followed by sodium hydroxide solution (or use a flame test showing a brick-red / orange-red flame) to confirm calcium ions — award the mark for either: [flame test] hold a nichrome wire in the solution and place in a Bunsen flame, observation: brick-red / orange-red flame; OR [precipitation] add excess sodium hydroxide, observation: white precipitate

## Key terms

- [sulfate ion](https://www.gradenine.co.uk/glossary/sulfate-ion)

## 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-geologist-discovers-a-mineral-sample-228b3331) · Published by Druglandscape Ltd.