A 0.750 g sample of an unknown substance is dissolved in 20.0 g of benzene, C6H6. The freezing point of the solution is 4.53 oC. Calculate the molar mass of the substance. The normal freezing point for benzene is 5.53 oC and Kf is 5.12 oC/m.

Answer 1

delta T = Kf*m
Calculate m
m = mols/kg solvent.
calculate moles.
moles = grams/molar mass
calculate molar mass.