a and b are van der Waals' constants for gases. Chlorine is more easily liquefied than ethane because

Van der waals constant ′a′ is a mixture of inter molecular forces and ′b′ is a measure of molecular size. A greater value of ′a′ and lesser value of ′b′ supports liquefication of a given gas. Therefore, chlorine is more easily liquefied than ethane because ′a′ for Cl₂​> ′a′ for C₂​H₆​ but ′b′ for Cl₂​< ′b′ for 

C₂​H₆​.