Please help me calculate the molecular weight of this problem!?

Question

A 10.180 g sample of benzophenone is found to freeze at 46.8 degrees C. When 0.680 g of an unknown are added to the 10.180 g of benzophenone the resulting solution is found to freeze at 42.6 degrees C. Calculate the molecular weight for the unknown. KF for benzophenone is 9.80 degrees C/m.

Not sure at all how to do this one?!!!

Answer 1

Actually

delta T = 46.8 - 42.6 =4.2

4.2 = 9.80 x m

m =0.429 = moles solute / 0.010180 Kg

moles solute =0.00436

Molar mass = 0.680 g / 0.00436 mol =155.9 g/mol

Answer 2

delta T = 46.8 - 42.6 =4.2

4.2 = 9.80 x m

m =0.429 = moles solute / 0.010180 Kg

moles solute =0.00436

Molar mass = 0.680 g / 0.00436 mol =155.9 g/mol