# A student carries out a reaction to produce copper sulfate crystals. The theoretical yield of copper sulfate is 25.0 g, but the student only collects 18.5 g of crystals. Explain why the actual yield is less than the theoretical yield, and describe TWO reasons that could account for this difference in this type of practical.

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

> Percentage yield is used to compare the actual yield of a product with the theoretical yield. The actual yield is almost always less than the theoretical yield.

## Mark scheme (4 marks)

1. The actual yield is less than the theoretical yield because not all of the reactant is converted into product / the reaction may be incomplete
2. Some product may be lost during transfer between containers / filtering / evaporating
3. Side reactions may occur, producing by-products instead of the desired product
4. The percentage yield is less than 100% because the actual yield (18.5 g) is less than the theoretical yield (25.0 g), showing that not all possible product was obtained

## 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 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-a368d13d) · Published by Druglandscape Ltd.