At low pressure and high temperature, real gases behave like ideal gases. Accordingly, Van der Waals equation is modified as:

${\text{pV}}_{\text{m}}=\text{RT}$ (for 1 mole)

$\because$ At low pressure and high temperature, the terms $\frac{\text{a}}{{\text{V}}^{\text{2}}}$ and $\text{b}$ becomes very small as compared to $\text{p}$ and $\text{V}$.