Two van der Waals gases have the same value of `b` but different values of `a`. Which of these will occupy greater volume under identical conditions. If the gases have the same value of `a` but different values of `b`, which of them will be more compressible?

Explanation

When two gases have the same value of `b` but different values of `a`, the gas having a larger value of `a` will occupy lesser volume. This is because the gas with a larger value of `a` will have larger forces of attraction and hence lesser distance between its molecules.
When two gases have the same volume of `a` but different values of `b`, the smaller the value of `b`, the larger the compressibility because the gas with the smaller value of `b` will occupy lesser volume and hence will be more compressible.