# A farmer buys a liquid weedkiller product from a garden centre. The label states that it contains several different active ingredients mixed together in carefully measured quantities to give the product its required properties. Explain what type of mixture this weedkiller product is, and describe how paper chromatography could be used to show that the product contains more than one active ingredient.

> WJEC A-Level Chemistry (Wales) — 1.1 Atoms, molecules and stoichiometry · Explain and Describe · 5 marks

## Mark scheme (5 marks)

1. The weedkiller is a formulation
2. A formulation is a mixture designed for a particular use / made up of exact quantities of pure substances
3. In paper chromatography, paper acts as the stationary phase and a solvent (mobile phase) carries the mixture up the paper
4. Different substances travel different distances up the paper because they have different solubilities in the solvent
5. More than one spot on the chromatogram shows the product contains more than one substance / active ingredient

## Key terms

- [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 and Describe" 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-farmer-buys-a-liquid-weedkiller-8bb908cc) · Published by Druglandscape Ltd.