Under what conditions does a real gas obey the relation $PV = RT$?

In Van der Waals equation $\left( P + \frac{a}{V^2} \right)(V - b) = RT$,what do $a$ and $b$ represent?

If the radius of an $O_{2}$ molecule is $40 \; \mathring{A}$,$T = 27^{\circ}C$,and $P = 1 \; \text{atm}$,find the relaxation time.

Ten small planes are flying at a speed of $150 \ km/h$ in total darkness in an air space that is $20 \times 20 \times 1.5 \ km^3$ in volume. You are in one of the planes, flying at random within this space with no way of knowing where the other planes are. On the average, about how long a time will elapse between near collisions with your plane? Assume for this rough computation that a safety region around the plane can be approximated by a sphere of radius $10 \ m$.

The value of $C_p - C_v = 1.00 R$ for a gas in state $A$ and $C_p - C_v = 1.06 R$ in another state $B$. If $P_A$ and $P_B$ denote the pressure and $T_A$ and $T_B$ denote the temperature in the two states,then:

Every real gas behaves as an ideal gas: