A gas described by van der Waals equation

Options

A. (a) behaves similar to an ideal gas in the limit of large molar volumes.
B. (b) behaves similar to an ideal gas in the limits of large pressures.
C. (c) is characterised by van der Waals coefficients that are dependent on the identity of the gas but are independent of the temperature.
D. (d) has pressure that is lower than the pressure exerted by the same gas behaving ideally.

Explanation

If the molar volume is very large, the effect of attractive forces as well as molecular size is almost nil. Both the pressure correction and volume can be neglected. Therefore, the gas behaves ideally, i.e., `PV=nRT`. The gas in van der Waals equation is characterised by van der Waals coefficients that are dependent on the identity of the gas but are idependent of the temperature, or the effect of the temperature on these constants is neglected. In case of a real gas, the molecules strike the walls of the container with less force because they are attracted by other molecules. Therefore, pressure in a real gas is always less than the pressure in an ideal gas where the molecules collide with a larger impact.