# A student uses paper chromatography to separate the dyes present in a sample of plant extract. The student runs the chromatogram using two different solvents. In the first solvent, three spots are visible. In the second solvent, four spots are visible. Explain what the student can conclude about the composition of the plant extract and how paper chromatography separates the different dyes.

> OCR A-Level Chemistry B: Salters (H433) — 6.3 Analysis (chromatography, NMR) · Explain · 5 marks

> Paper chromatography can be used to separate and identify the components of a mixture. Each component travels a different distance up the chromatography paper depending on how it interacts with the stationary phase and the mobile phase.

## Mark scheme (5 marks)

1. The plant extract contains a mixture of (at least four) different dyes / components
2. The second solvent separates the components more effectively / reveals more components, so the number of components is at least four
3. The mobile phase (solvent) carries the dyes up the paper
4. Dyes that are more soluble in the solvent / interact more strongly with the mobile phase travel further up the paper
5. Dyes that interact more strongly with the stationary phase (paper) travel less far / are retained more

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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-student-uses-paper-chromatography-to-e076f7af) · Published by Druglandscape Ltd.