# A student prepares a sample of copper(II) sulfate solution by adding dilute sulfuric acid to an excess of copper(II) carbonate powder. She then heats the mixture and observes that the fizzing stops before all the solid has dissolved. She filters the mixture to obtain a clear blue solution. Explain why the student added an excess of copper(II) carbonate and why she filtered the mixture at the end.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 3.4 Acids, alkalis and salts · Explain · 4 marks

> Copper(II) carbonate reacts with dilute sulfuric acid in a neutralisation reaction to produce copper(II) sulfate, water and carbon dioxide.

## Mark scheme (4 marks)

1. Excess copper(II) carbonate is added to ensure all the acid is used up / reacted
2. If acid remained in solution, the final salt solution would be impure / contaminated with acid
3. Filtration is carried out to remove the excess / unreacted copper(II) carbonate solid
4. This leaves only the copper(II) sulfate solution in the filtrate / gives a pure salt solution

## Key terms

- [excess](https://www.gradenine.co.uk/glossary/excess)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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-prepares-a-sample-of-0504bf78) · Published by Druglandscape Ltd.