Chemistry › Section I · Gases › Topic I.6
Non-ideal gas behaviour
No real gas obeys PV = nRT exactly. Real molecules take up space and attract each other, and under high pressure or at low temperature those effects grow large enough to matter. Knowing when and why the ideal gas law fails tells you when you can trust it.
In this topic
- Where the ideal model breaks down
- Measuring non-ideality: the compressibility factor
- How Z changes with pressure
- Low temperature and condensation
- The van der Waals equation
- Reading the van der Waals constants
- Worked example: carbon dioxide at moderate pressure
- Worked example: helium at high pressure
- Common mistakes to avoid
- Key takeaways
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