# A student tests an unknown solution using universal indicator and litmus paper. The universal indicator turns orange and the litmus paper turns red. Describe what these results tell the student about the unknown solution, and explain why scientists prefer to use universal indicator rather than litmus paper when testing solutions.

> Eduqas GCSE Chemistry — C8 Chemical analysis · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. The solution is acidic
2. Universal indicator gives a pH value / indicates the strength or concentration of the acid (e.g. pH 4–5 / weakly acidic / not strongly acidic)
3. Litmus only shows whether a solution is acidic or alkaline (cannot give a pH value)
4. Universal indicator is a mixture of dyes / shows a range of colours corresponding to different pH values on the pH scale (pH 1–14)

## Key terms

- [universal indicator](https://www.gradenine.co.uk/glossary/universal-indicator)
- [litmus](https://www.gradenine.co.uk/glossary/litmus)

## Related

- [Revision notes for Eduqas GCSE Chemistry](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-tests-an-unknown-solution-de41b0ac) · Published by Druglandscape Ltd.