# A pharmacy technician is making a painkiller tablet. The tablet contains four different substances, each present in a carefully measured quantity to ensure the tablet has the required properties. The technician uses paper chromatography to check that one of the substances, a white pain-relieving compound, is pure before it is added to the tablet. The chromatogram produced shows a single spot. Explain what the single spot tells the technician about the compound, and describe how paper chromatography separates the substances in a mixture.

> WJEC A-Level Chemistry (Wales) — 1.6 Kinetics · Explain · 5 marks

> A pharmacy technician is making a painkiller tablet. The tablet contains four different substances, each present in a carefully measured quantity to ensure the tablet has the required properties. The technician uses paper chromatography to check that one of the substances, a white pain-relieving compound, is pure before it is added to the tablet. The chromatogram produced shows a single spot.

## Mark scheme (5 marks)

1. The painkiller tablet is a formulation (a mixture designed for a particular use / made up of exact quantities of pure substances).
2. A single spot shows the compound is pure (contains only one substance / is not a mixture).
3. If the compound were impure / a mixture, it would produce more than one spot.
4. In paper chromatography, the solvent (mobile phase) carries the substances up the paper (stationary phase).
5. Substances separate because they differ in how soluble they are in the mobile phase / how strongly they are attracted to the stationary phase — the more soluble a substance, the further up the paper it travels.

## Key terms

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

## Related

- [Revision notes for WJEC A-Level 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-pharmacy-technician-is-making-a-9e3a9c1c) · Published by Druglandscape Ltd.