# A sports drink manufacturer claims that the orange colouring used in their drink is a single pure substance. A student carries out paper chromatography on the orange colouring using two different solvents. In solvent A, the orange colouring produces three separate spots. In solvent B, the orange colouring produces a single spot. Explain what the results in each solvent tell us about the orange colouring, and state what the student should conclude overall about the manufacturer's claim.

> WJEC A-Level Chemistry (Wales) — 1.2 Electronic structure · Explain · 5 marks

## Mark scheme (5 marks)

1. The three spots in solvent A show that the orange colouring is a mixture (containing more than one substance/compound)
2. The three substances travel different distances because they have different solubilities in the mobile phase (solvent A) / distribute differently between the mobile and stationary phases
3. A pure compound produces a single spot in all solvents, so the single spot in solvent B alone does not prove purity
4. The result from solvent A (three spots) is evidence that the colouring is a mixture, so the manufacturer's claim is incorrect / false
5. The Rf values of the three spots (in solvent A) could be used to help identify the individual substances present in the mixture

## Key terms

- [pure substance](https://www.gradenine.co.uk/glossary/pure-substance)
- [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-sports-drink-manufacturer-claims-that-89afb703) · Published by Druglandscape Ltd.