# A student is investigating how the concentration of hydrogen peroxide solution affects the volume of oxygen gas produced when manganese(IV) oxide is used as a catalyst. Describe how the student should carry out a fair and safe investigation, including how they would collect and measure the volume of oxygen produced.

> OCR A-Level Chemistry A (H432) — 1.1 Practical skills assessed · Describe · 5 marks

> Hydrogen peroxide decomposes into water and oxygen gas. Manganese(IV) oxide acts as a catalyst for this reaction. A student wants to investigate how changing the concentration of hydrogen peroxide affects the total volume of oxygen gas collected.

## Mark scheme (5 marks)

1. Keep all variables the same except the concentration of hydrogen peroxide (e.g. same volume of hydrogen peroxide solution, same mass of manganese(IV) oxide, same temperature)
2. Collect the oxygen gas using a gas syringe or by displacement of water (inverted measuring cylinder over water trough)
3. Record the total / final volume of oxygen gas collected for each concentration
4. Repeat each concentration at least once (and calculate a mean) to improve reliability
5. Safety precaution appropriate to this investigation, e.g. wear safety goggles / handle hydrogen peroxide with care as it is an irritant / work in a well-ventilated area

## Key terms

- [concentration](https://www.gradenine.co.uk/glossary/concentration)
- [catalyst](https://www.gradenine.co.uk/glossary/catalyst)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-investigating-how-the-ac498b5e) · Published by Druglandscape Ltd.