# A pharmacist is checking the purity of a painkiller tablet. She dissolves a small amount of the tablet in a solvent and carries out paper chromatography alongside a sample of the pure active ingredient. The painkiller sample produces three separate spots on the chromatogram, whilst the pure active ingredient produces only one spot. Explain what these results tell the pharmacist about the painkiller tablet, and explain how paper chromatography causes substances in a mixture to separate.

> WJEC GCSE Chemistry (Wales) — 1.4 The ever-changing Earth · Explain · 4 marks

## Mark scheme (4 marks)

1. The painkiller tablet is a mixture / is not a pure substance
2. The three spots indicate three different compounds / substances are present in the tablet
3. In paper chromatography, the mobile phase (solvent) carries the substances up the stationary phase (paper)
4. Substances separate because they have different solubilities in the mobile phase / more soluble substances travel further up the paper

## Key terms

- [paper chromatography](https://www.gradenine.co.uk/glossary/paper-chromatography)
- [mixture](https://www.gradenine.co.uk/glossary/mixture)

## Related

- [Revision notes for WJEC GCSE Chemistry (Wales)](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-pharmacist-is-checking-the-purity-a4207767) · Published by Druglandscape Ltd.