9 K kg mol
 × 2 g × 1000 g kg
25 g × 1 62 K
= 241 98 g mol–1
Thus, experimental molar mass of benzoic acid in benzene is
= 241 98 g mol–1
Now consider the following equilibrium for the acid:
2 C6H5COOH  ⇌   (C6H5COOH)2
If x represents the degree of association of the solute then we would
have (1 – x ) mol of benzoic acid left in unassociated form and
correspondingly 2
x  as associated moles of benzoic acid at equilibrium