# A student tests three unknown solutions to identify the halide ions present. They add a few drops of silver nitrate solution to each unknown solution and observe the colour of the precipitate formed. Solution A gives a white precipitate, Solution B gives a cream precipitate, and Solution C gives a yellow precipitate. Explain how these observations allow the student to identify which halide ion is present in each solution.

> OCR GCSE Chemistry A: Gateway Science (J248) — C4.2 Identifying the products of chemical reactions · Explain · 4 marks

> Silver nitrate solution reacts with halide ions to form silver halide precipitates. Silver chloride is white, silver bromide is cream, and silver iodide is yellow.

## Mark scheme (4 marks)

1. Solution A contains chloride ions (Cl⁻)
2. Solution B contains bromide ions (Br⁻)
3. Solution C contains iodide ions (I⁻)
4. The different coloured precipitates are formed because each halide ion reacts with silver ions to form a different, insoluble silver halide compound

## Key terms

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

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-tests-three-unknown-solutions-3e0e187e) · Published by Druglandscape Ltd.