For a gas,deviation from ideal behaviour is maximum at

Which of the following relations between the van der Waals constant $b$ and the radius of a spherical molecule $r$ is correct?

At high temperature and low pressure,the Vander Waal's equation is reduced to

Four gases $P, Q, R$ and $S$ have almost same values of $b$ but their $a$ values ($a, b$ are van der Waals' constants) are in the order $Q < R < S < P$. At a particular temperature among the four gases, the most liquefiable one is

Among the gases $a$,$b$,$c$,$d$,$e$ and $f$,the gases that show only positive deviation from ideal behavior at all pressures in the graph are

If the compressibility factor $(Z)$ is greater than unity,then which of the following is true for the molar volume $(V_m)$ of a gas at $NTP$?