# A student suspects that a white powder could be either sodium chloride or sodium carbonate. Describe how the student could use chemical tests to identify which substance the white powder is. Include the expected observations for each substance.

> Eduqas GCSE Chemistry — C8 Chemical analysis · Describe · 4 marks

## Mark scheme (4 marks)

1. Add dilute hydrochloric acid (or dilute acid) to the powder
2. Sodium carbonate produces bubbles / fizzing / effervescence whereas sodium chloride does not react
3. To confirm, test the gas produced with limewater
4. Limewater turns milky / cloudy, confirming the gas is carbon dioxide and therefore the powder is sodium carbonate

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Chemistry](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-suspects-that-a-white-54c7189f) · Published by Druglandscape Ltd.