Question

When real gases obey the ideal gas equation $PV=nRT$?

Answer 1

Real gas obeys van der Waals equation

$(P+\frac{n^{2}a}{V^2})(V-nb)=nRT$

Low pressure decreases the effect of the finite size of real particles by increasing the volume around each particle. High temperature provides enough kinetic energy to particles to overcome real attractions existing between particles.

Thus at high temperature and low-pressure volume and pressure correction terms becomes negligible.

Hence Van der Waal equation becomes approximately $PV=nRT$.

So gases behave ideally at high temperatures and low pressure.