# A student carries out a flame test on an unknown solution and observes a lilac flame. The student then adds dilute hydrochloric acid followed by barium chloride solution to a separate sample of the unknown solution, producing a white precipitate. Identify the metal ion and the negative ion present in the unknown solution. Explain how the results of the two tests support your answers.

> AQA GCSE Chemistry (8462) — 4.8.3 Identification of ions by chemical and spectroscopic means (Chem only) · Explain · 4 marks

## Mark scheme (4 marks)

1. The metal ion is potassium (K⁺)
2. A lilac / purple flame colour indicates the presence of potassium ions
3. The negative ion is sulfate (SO₄²⁻)
4. A white precipitate with barium chloride solution (after adding hydrochloric acid) indicates the presence of sulfate ions

## Key terms

- [flame test](https://www.gradenine.co.uk/glossary/flame-test)
- [metal ion](https://www.gradenine.co.uk/glossary/metal-ion)
- [white precipitate](https://www.gradenine.co.uk/glossary/white-precipitate)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-carries-out-a-flame-51780d28) · Published by Druglandscape Ltd.