Explain the physical significance of vander Waals parameter.

Explanation

Vander Waals equation : ` [ P + (an^2)/( V^2)] (V-nb) = nRT `
Where P = Pressure of the gas
n = Number of moles of the gas .
a, b = Vander Waals parameters (or) empirical parameters
V = Volume of the container
R = Gas constant
T = Absolute temperature
Units of .a.:- bar `"lit "^(-2)`mole`""^(-2)`
Units of .b.:- lit. `mol^(-1)`
Significance :-
` to` .a. is the measure of magnitude of inter molecular forces (attractive) with in the gas and is independent of temperature and pressure. If .a. value is high the gas can be easily liquified.
` to `.b. is the effective volume of the gas molecule. It indicates the effective size of the gas molS ecules. If the value of .b. is constant over a long range of temperature and pressure then the gas cannot be compressed easily.