Question

What are units of a and b which are vander waal s constant?

Answer 1

a=(Pressure ×Volume^2) /moles^2

The constant a provides a correction for the intermolecular forces.If the pressure is expressed in atmospheres are volume in litres the unit of 'a' will be atmL^2/mol^2 Or atm dm^6/mol^2 Or Nm^4/mol^2

Constant b is a correction for finite molecular size and its value is the volume of one mole of the atoms or molecules. Or Otherwise It is the effective volume occupied by molecules present in one mole of the gas. Hence the unit of 'b' is same as that of volume. L/mol or m^3/mol.

Hope you understand.