# Sodium carbonate has the formula Na₂CO₃. State the number of atoms of each element present in one formula unit of sodium carbonate, and use this information to explain the difference between an empirical formula and a molecular formula.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.5 Chemical formulae, equations and calculations · Explain · 4 marks

> Sodium carbonate, Na₂CO₃, is a white solid used in glass manufacturing. Its empirical formula is NaCO₃ and its molecular formula is Na₂CO₃.

## Mark scheme (4 marks)

1. Sodium carbonate contains 2 sodium atoms, 1 carbon atom, and 3 oxygen atoms (per formula unit)
2. The empirical formula shows the simplest whole number ratio of atoms of each element in a compound
3. The molecular formula shows the actual number of atoms of each element in one molecule / formula unit of the compound
4. For Na₂CO₃, the empirical formula (NaCO₃) cannot be simplified further to a simpler whole number ratio / the molecular formula (Na₂CO₃) shows twice as many atoms as the empirical formula

## Key terms

- [empirical formula](https://www.gradenine.co.uk/glossary/empirical-formula)
- [molecular formula](https://www.gradenine.co.uk/glossary/molecular-formula)
- [atom](https://www.gradenine.co.uk/glossary/atom)

## 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/sodium-carbonate-has-the-formula-na-co-18892506) · Published by Druglandscape Ltd.