# A student carries out a reaction to produce copper sulfate. The theoretical yield of copper sulfate is 20 g, but the student only collects 15 g. Explain why the actual yield is less than the theoretical yield, giving two reasons.

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

> In industry and in the laboratory, chemical reactions rarely produce the maximum possible amount of product.

## Mark scheme (4 marks)

1. The actual yield is less than the theoretical yield because some product may be lost during the practical process (e.g. during filtering, transferring or evaporating)
2. The reaction may be reversible, so it does not go to completion and not all reactants are converted to products
3. Percentage yield is calculated by dividing the actual yield by the theoretical yield and multiplying by 100
4. The percentage yield in this case is 75%

## Key terms

- [actual yield](https://www.gradenine.co.uk/glossary/actual-yield)
- [theoretical yield](https://www.gradenine.co.uk/glossary/theoretical-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-carries-out-a-reaction-c0c2e1df) · Published by Druglandscape Ltd.