At $S.T.P.$,if the compressibility factor $(Z)$ of a gas is less than $1$,then which of the following is true?

Consider the following gases and their corresponding $ 'a'$ values given in parentheses: $CH_4 (2.25), N_2 (1.35), O_2 (1.36)$,and $CO (1.46)$. Which of these gases will be the most difficult to liquefy?

Give the difference between an Ideal Gas and a Real Gas.

If the compressibility factor $(Z)$ of a real gas is $1.05$ at $STP$,what is the molar volume of the real gas (in $dm^3$)?

Excluded volume $(v)$ per molecule is related to the van der Waals constant $'b'$ in the following way:

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: