Liquid Solution

Benzoic acid molecules undergo dimerisation in benzene. 2.44 g of benzoic acid when dissolved in 30 g of benzene caused depression in freezing point of 2 K . What is the percentage of association of it?

(Given $K_f\left(\mathrm{C}_6 \mathrm{H}_6\right)=5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$; molar mass of benzoic acid $=122 \mathrm{~g} \mathrm{~mol}^{-1}$ )