Benzoic acid () is dissolved in benzene. The experimentally determined molar mass based on colligati — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

The normal theoretical molar mass of benzoic acid is $122\text{ g mol}^{-1}$. The van't Hoff factor is $i = \frac{M_{normal}}{M_{obs}} = \frac{122}{244} = 0.5$. The association formula is $i = 1 + \alpha(\frac{1}{n} - 1)$. If we assume complete dimerization ($n=2, \alpha=1$), then $i = 1 + 1(\frac{1}{2} - 1) = 0.5$. Thus, it exists predominantly as a dimer with nearly $100\%$ association.