# A student carries out a reaction to produce iron oxide. The theoretical yield of iron oxide is 8.0 g, but the student only obtains 6.0 g of iron oxide. Explain why the actual yield is less than the theoretical yield, and describe what is meant by percentage yield.

> Edexcel GCSE Chemistry (1CH0) — 5.2 Quantitative analysis (Chem only) · Explain · 4 marks

> In industrial and laboratory chemistry, reactions rarely produce the maximum possible amount of product. Chemists use percentage yield to compare how much product was actually obtained with how much could theoretically have been made.

## Mark scheme (4 marks)

1. The actual yield is less than the theoretical yield because the reaction may be incomplete / not all reactants are converted to products
2. The actual yield may be reduced due to side reactions producing unwanted by-products
3. The actual yield may be reduced due to loss of product during transfer between containers / filtering / evaporating
4. Percentage yield is the percentage ratio of the actual yield compared with the theoretical yield (actual yield ÷ theoretical yield × 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 Edexcel GCSE Chemistry (1CH0)](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-carries-out-a-reaction-cb1d748f) · Published by Druglandscape Ltd.