# A pharmacist is checking whether a newly manufactured painkiller tablet is a pure substance or a formulation. She measures the melting point of the active ingredient and also carries out paper chromatography on a dissolved sample of the tablet. Explain how the results of both tests could be used to determine whether the tablet contains a single pure substance or a formulation.

> Eduqas A-Level Chemistry — 1.1 Atoms, molecules and stoichiometry · Explain · 5 marks

> A pharmacist tests a painkiller tablet using melting point apparatus and paper chromatography to check its composition.

## Mark scheme (5 marks)

1. A pure substance has a sharp (single) melting point / melts at one specific temperature
2. A formulation / mixture melts over a range of temperatures, so a broad melting range indicates it is not a pure substance
3. In paper chromatography, a pure substance produces a single spot
4. A formulation / mixture produces more than one spot because it contains more than one compound
5. The Rf value of each spot can be compared to known values to identify the substances present in the tablet

## Key terms

- [pure substance](https://www.gradenine.co.uk/glossary/pure-substance)
- [formulation](https://www.gradenine.co.uk/glossary/formulation)
- [melting point](https://www.gradenine.co.uk/glossary/melting-point)
- [paper chromatography](https://www.gradenine.co.uk/glossary/paper-chromatography)

## Related

- [Revision notes for Eduqas A-Level Chemistry](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-pharmacist-is-checking-whether-a-1dc85fd9) · Published by Druglandscape Ltd.