The van der Waals equation is an equation of state for a fluid composed of particles that have a non-zero volume and a pairwise attractive inter-particle force (such as the van der Waals force). The equation is

Physical significance of ‘a’: ‘a’ is a measure of the magnitude of intermolecular attractive forces between the particles

Physical significance of ‘b’:

‘b’ is the volume excluded by a mole of particles

  p is the pressure of fluid

V  is the total volume of container containing the fluid