chemistry
posted by Jim_R .
10.0 g sample of pdichlorobenzene, a component of mothballs, is
dissolved in 80.0 g of benzene, C6H6. The freezingpoint of the solution is
1.20oC. The freezing point of benzene is 5.48oC. The molal freezing â€“point
constant, kf, for benzene is 5.12oC/m. Calculate the apparent molar
mass of pdichlorobenzene.

delta T = i*Kf*m
You know delta T, i = 1 and you know Kf. Solve for m, molality.
Then m = moles/kg solvent.
You know m and kg solvent, solve for moles.
Then moles = grams/molar mass. You know moles and grams, solve for molar mass.
Post your work if you get stuck. 
k thanks
Its a practice question for my final exam. No answer is given.