# Carbon dioxide, CO₂, is a gas produced during respiration. Describe how the relative formula mass of carbon dioxide is determined, and state the relative formula mass of carbon dioxide. (Relative atomic masses: C = 12, O = 16.)

> Cambridge International IGCSE Chemistry (0620) — 3.2 Relative masses of atoms and molecules · Describe · 4 marks

## Mark scheme (4 marks)

1. Relative formula mass is found by adding together the relative atomic masses of all the atoms in the formula
2. Correct identification that there is one carbon atom contributing 12 and two oxygen atoms each contributing 16
3. Correct calculation shown: 12 + 16 + 16 or 12 + (2 × 16)
4. Relative formula mass of carbon dioxide = 44

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/carbon-dioxide-co-is-a-gas-a8ca45b2) · Published by Druglandscape Ltd.