What is the correction term in the pressure for real gas in comparison to the ideal gas?

At a temperature of $27\,^{\circ}C$,if the volume of $2\, \text{moles}$ of $NH_3$ gas is $5\, L$ according to the van der Waals equation,what will be its pressure in $atm$? ($a = 4.17$,$b = 0.03711$)

At $300 \ K$,the compressibility factor of $1 \ mole$ of a gas is $1.1$. Its pressure is $2.706 \ atm$. What is its volume in $L$? (Given $R=0.082 \ L \ atm \ mol^{-1} \ K^{-1}$).

Which of the following statements is false based on the provided graph of compressibility factor $Z$ versus pressure $P$?

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

Helium is suitable for gas thermometry at low temperatures because of its ...