# Zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas. A student carries out this reaction in an open beaker and observes that the mass of the reaction mixture decreases during the reaction. Explain why the mass decreases, and describe what the student could do to show that mass is conserved in this reaction.

> Edexcel GCSE Chemistry (1CH0) — 1.8 Calculations involving masses · Explain · 4 marks

## Mark scheme (4 marks)

1. Hydrogen gas is produced during the reaction
2. The hydrogen gas escapes / is released into the surroundings from the open beaker
3. The student should carry out the reaction in a closed / sealed container
4. The total mass before the reaction would equal the total mass after the reaction, showing mass is conserved

## Key terms

- [hydrogen gas](https://www.gradenine.co.uk/glossary/hydrogen-gas)
- [reaction mixture](https://www.gradenine.co.uk/glossary/reaction-mixture)

## 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/zinc-reacts-with-hydrochloric-acid-to-e9cf9d09) · Published by Druglandscape Ltd.