Question

Which of the following are correct statements ?

Answer 1

Van der Waals constant $a$ is a indirect measure of attractive force. Gases with higher values of $a$ can be easily liquified.
Van der Waals constant $b$ is also called co-volume or excluded volume. It is the effective volume of a gas. When gas molecules have constant value of $b$ over wider range of temperature and pressure, the gas molecules are incompressible.
$b$ has units $Lmo{l}^{-1}$ or $m{l}^{3}mo{l}^{-1}$.
The units of $a$ are $atm{L}^{2}mo{l}^{-1}$.