# What are 2 assumptions made by ideal gas laws that are violated by real gases?

Jan 2, 2018

(i) That there is negligible interaction between gas molecules, and (ii) that they are infinitesimally small relative to their container.

The van der Waals equation accounts for these with characteristic quantitative modifiers for each molecule of gas,

$\left[P + a {\left(\frac{n}{V}\right)}^{2}\right] \left(\frac{V}{n} - b\right) = R T$

where $a$ accounts for (i) and $b$ accounts for (ii).

In English, the pressure will increase and the volume will decrease relative to the ideal gas equation,

$P V = n R T$