# A student reacts iron with sulfur to produce iron sulfide. The theoretical yield of iron sulfide is 44 g, but the student only obtains 33 g. Explain why the actual yield of a chemical reaction is often less than the theoretical yield, and describe what is meant by percentage yield.

> AQA GCSE Chemistry (8462) — 4.3.3 Yield and atom economy of chemical reactions · Explain · 4 marks

> Iron reacts with sulfur to produce iron sulfide: Fe + S → FeS

## Mark scheme (4 marks)

1. Percentage yield is the actual yield expressed as a percentage of the theoretical yield
2. One valid reason why actual yield is less than theoretical yield — e.g. the reaction may be reversible / may not go to completion
3. A second valid reason — e.g. some product may be lost during collection / purification / transfer
4. The percentage yield in this reaction is 75% (33 ÷ 44 × 100)

## Key terms

- [actual yield](https://www.gradenine.co.uk/glossary/actual-yield)
- [theoretical yield](https://www.gradenine.co.uk/glossary/theoretical-yield)
- [percentage yield](https://www.gradenine.co.uk/glossary/percentage-yield)

## 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-reacts-iron-with-sulfur-b2fb1317) · Published by Druglandscape Ltd.