Which gas among the following is the easiest to liquify?

The van der Waals constants for $HCl$ gas are $a = 3.6 \ atm \ L^2 \ mol^{-2}$ and $b = 40 \ mL \ mol^{-1}$. The critical temperature of the gas is : ............. $K$ [ $R = 0.08 \ atm \ L \ K^{-1} \ mol^{-1}$ ]

$A$ gas such as carbon monoxide would be most likely to obey the ideal gas law at

What is the difference in the pressure-volume $(P-V)$ graph (at constant $T$) for a real gas and an ideal gas?

Under which conditions does a real gas show maximum deviation from ideal gas behavior?

$A$ real gas would be most likely to obey the ideal gas laws at