The compressibility factor $(Z)$ of a gas is less than unity at $STP$,then:

Van der Waals equation for a gas is stated as,
$p = \frac{nRT}{V - nb} - a\left( \frac{n}{V} \right)^2$
This equation reduces to the perfect gas equation,$p = \frac{nRT}{V}$,when:

When is deviation more in the behaviour of a gas from the ideal gas equation $PV = nRT$?

The compressibility factor $(z)$ is lower for $NH_3$ and $CO_2$ gases than that of $N_2$ gas, because

The unit of the Van der Waals constant '$a$' is .......

Pressure exerted by $1 \, mole$ of methane in a $0.25 \, L$ container at $300 \, K$ using van der Waals equation is ............... $atm$ (given $a = 2.253 \, atm \, L^2 \, mol^{-2}, b = 0.0428 \, L \, mol^{-1}$):