Question

3 g of benzoic acid is added to 25 g of benzene. \( \Delta T_f = 2.5\,\text{K} \) and \( K_f \) of benzene is 5. What is the experimental molecular mass of benzoic acid?

Hint:

If calculated molar mass is double the theoretical formula mass, it strongly implies the solute undergoes 100% dimerization in the solvent (van't Hoff factor $i = 0.5$).

Answer 1