At Boyle's temperature,the compressibility factor $Z$ for a real gas is:

The pressure $(p)$ and volume $(V)$ isotherm of a van der Waals' gas,at the temperature at which it undergoes gas to liquid transition,is correctly represented by

The compressibility factor of a gas is less than $1$ at $STP$. Its molar volume $V_m$ will be

When does the graph of $p \propto \frac{1}{V}$ not result in a straight line?

$CH_4$ gas is behaving non-ideally. The compressibility factor for the gas is $1.5$ at $2 \ atm$ and $400 \ K$. Calculate the molar volume for the gas in $litre$. [Given $R = 0.08 \ L \ atm \ K^{-1} \ mol^{-1}$]

For real gases,the van der Waals equation is written as $\left( p + \frac{a n^2}{V^2} \right) (V - nb) = nRT$,where $a$ and $b$ are van der Waals constants. Two sets of gases are:
$(I)$ $O_2, CO_2, H_2, He$
$(II)$ $CH_4, O_2, H_2$
The gases given in set-$I$ are arranged in increasing order of $b$,and the gases given in set-$II$ are arranged in decreasing order of $a$. Select the correct order from the following: