Which equation shows the correct form of the Berthelot equation?

$A$ gas at $350 \; K$ and $15 \; bar$ has a molar volume $20$ percent smaller than that for an ideal gas under the same conditions. The correct option about the gas and its compressibility factor $(Z)$ is

Pressure versus volume graph for a real gas and an ideal gas are shown in the figure. Answer the following questions on the basis of this graph:
$(i)$ Interpret the behaviour of real gas with respect to ideal gas at low pressure.
$(ii)$ Interpret the behaviour of real gas with respect to ideal gas at high pressure.
$(iii)$ Mark the pressure and volume by drawing a line at the point where real gas behaves as an ideal gas.

Identify the correct variation of pressure $(p)$ and volume $(V)$ of a real gas $(A)$ and an ideal gas $(B)$ at constant temperature. ($y = p$; $x = V$)

Which gas among the following is the easiest to liquify?

Van der Waals constants '$a$' and '$b$' are related with..... respectively.