What are units of Vander waals constant \'a\' and \'b\'? What is their significance?

What are units of Vander waals constant \'a\' and \'b\'? What is their

1.	What are units of Vander waals constant \'a\' and \'b\'? What is their significance?
Answer» unit of a: atm L^2 mol^-2 or bar dm^6 mol^-1unit of b: L mol^-1 or dm^3 mol^-1