# Explain why the ideal gas equation becomes less accurate at low temperatures when applied to a sample of sulfur dioxide gas.

> IB DP Chemistry Higher Level (2023 syllabus) — S1.5 Ideal gases · Explain · 4 marks

## Mark scheme (4 marks)

1. At low temperatures, the average kinetic energy of SO₂ molecules is lower / molecules move more slowly.
2. Intermolecular (attractive) forces between SO₂ molecules become significant / are not negligible.
3. Molecules do not have sufficient kinetic energy to fully overcome these attractive forces, so they spend more time close together / are drawn towards one another.
4. The measured pressure is lower than that predicted by the ideal gas equation / the actual volume is lower than the ideal value, because the ideal gas equation assumes no intermolecular forces.

## Key terms

- [ideal gas equation](https://www.gradenine.co.uk/glossary/ideal-gas-equation)

## Related

- [Revision notes for IB DP Chemistry Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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