# A student makes a solution by dissolving potassium nitrate (KNO₃) in water. The concentration of the solution is 0.5 mol/dm³. Explain what is meant by a concentration of 0.5 mol/dm³ and describe how the concentration of this solution would change if more water were added to it.

> AQA GCSE Chemistry (8462) — 4.3.4 Using concentrations of solutions in mol/dm³ (Chem only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Concentration is the amount of substance in a certain volume of solution
2. 0.5 mol/dm³ means there are 0.5 moles of KNO₃ in every 1 dm³ (litre) of solution
3. Adding more water increases the volume of the solution
4. The concentration decreases because the same number of moles of KNO₃ is now in a larger volume

## Key terms

- [concentration](https://www.gradenine.co.uk/glossary/concentration)
- [mol/dm³](https://www.gradenine.co.uk/glossary/mol-dm)
- [solution](https://www.gradenine.co.uk/glossary/solution)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](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-makes-a-solution-by-a1db5b86) · Published by Druglandscape Ltd.