Colligative
properties calculations are used for this type of problem. Calculations are as
follows:
Look up the freezing point of benzene, then delta T = f.p.=3.5 = Kf*m
Solve for molality.
molality = moles/kg solvent
Solve for moles.
moles acetic acid = grams acetic acid/molar mass acetic acid
Solve for molar mass. You would expect to find 60 for the molar mass CH3COOH.