Question

Give an expression for the van der Waals equation. Give the significance of the constants used in the equation. What are their units?

Answer 1

Where n is the number of moles present and ‘a’’ b’ are known as van der Waals constants.

Significance of Van der Waals constants: 

Van der Waals constant ‘a’: ‘a’ is related to the magnitude of the attractive forces among the molecules of a particular gas. Greater the value of’a’ , more will be the attractive forces. 

Unit of’a’ = L² mol^-2

Van der Waals constant ‘b’: ‘b’ determines the volume occupied by the gas molecules which depends upon size of molecule. 

Unit of ‘b’ = L mol^-1