# A student reacts magnesium with hydrochloric acid to produce magnesium chloride. The theoretical yield of magnesium chloride is 19.0 g. The actual yield obtained is 13.3 g. Explain why the actual yield is less than the theoretical yield, and describe two steps the student could take during the experiment to improve the percentage yield.

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

> Percentage yield is calculated as: (actual yield ÷ theoretical yield) × 100. The student obtains a percentage yield of approximately 70%.

## Mark scheme (4 marks)

1. The actual yield is less than the theoretical yield because the reaction may be incomplete / not all the reactants are converted to products
2. Product can be lost during transfer between containers / during filtration / evaporation steps
3. One valid improvement: use a wash bottle / rinse all equipment with distilled water to recover any product left on the sides of the container
4. Second valid improvement: ensure the reaction is allowed to go to completion before collecting the product / use excess of one reactant to ensure the other is fully used up

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-reacts-magnesium-with-hydrochloric-5eae9973) · Published by Druglandscape Ltd.