# A student wants to separate the dyes in a sample of black ink using chromatography. Describe how the student would carry out this investigation and explain how the results show that black ink is a mixture of dyes.

> OCR A-Level Chemistry B: Salters (H433) — CD Colour by design · Describe and Explain · 5 marks

> Black ink appears to be a single colour, but it is actually made up of several different coloured dyes mixed together. Paper chromatography can be used to separate and identify the components of a mixture.

## Mark scheme (5 marks)

1. A spot/line of the black ink is placed near the bottom of the chromatography paper (baseline), above the level of the solvent
2. The paper is placed in a suitable solvent so the solvent travels up the paper
3. The chromatogram is removed and allowed to dry before results are analysed / the solvent front is marked
4. The black ink produces more than one spot/coloured spot at different heights on the chromatogram
5. Different dyes travel different distances up the paper because they have different solubilities in the solvent / different affinities for the paper, showing black ink is a mixture

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-wants-to-separate-the-5b1d6e16) · Published by Druglandscape Ltd.