# A student reacts calcium carbonate with excess hydrochloric acid. The equation for the reaction is: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. The student uses 5.0 g of calcium carbonate. The relative formula mass (Mr) of calcium carbonate is 100. The Mr of carbon dioxide is 44. Explain how the student can calculate the theoretical yield of carbon dioxide produced, and state the theoretical yield in grams.

> Edexcel A-Level Chemistry (9CH0) — 5.1 Calculations using moles · Explain · 5 marks

> Calcium carbonate reacts with hydrochloric acid in a 1:1 molar ratio with carbon dioxide as one of the products. The theoretical yield is the maximum possible mass of product that can be obtained from a reaction.

## Mark scheme (5 marks)

1. Calculate the number of moles of calcium carbonate used
2. Use the molar ratio from the balanced equation to determine moles of carbon dioxide
3. Use mass = moles × Mr to calculate the mass of carbon dioxide
4. States the correct theoretical yield of carbon dioxide
5. Explains that the theoretical yield is the maximum possible mass of product and that the actual yield is normally less

## Key terms

- [theoretical yield](https://www.gradenine.co.uk/glossary/theoretical-yield)
- [relative formula mass](https://www.gradenine.co.uk/glossary/relative-formula-mass)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-reacts-calcium-carbonate-with-d282b4ed) · Published by Druglandscape Ltd.