Final answer:
To calculate the molar mass of acetic acid in benzene, use the freezing point depression formula and the physical properties of benzene. The change in freezing point and molality are utilized to find the molar mass, which suggests the dimeric nature of acetic acid in nonpolar solvents like benzene.
Step-by-step explanation:
To calculate the molar mass of acetic acid (CH3COOH) dissolved in benzene (C6H6), we first need to use the freezing point depression formula, ΔTf = Kf · m, where ΔTf is the change in freezing point, Kf is the freezing point depression constant of the solvent (benzene has a Kf of 5.12 °C·kg/mol), and m is the molality of the solution. With the given freezing point of the solution as 3.5 °C and knowing that the freezing point of pure benzene is 5.5 °C, we can calculate the change in freezing point (ΔTf) to be 2 °C. We then find out the molality (m) of the solution using ΔTf and Kf. Finally, we use the molality and the mass of the solvent to calculate the molar mass of the solute. Based on the molar mass and the known structure of acetic acid, it might be suggested that acetic acid in benzene exists as dimers, which are pairs of acetic acid molecules held together by intermolecular attractions.