A solution containing 3.22g of solute in 40.0g of 1,4-dichlorobenzene and its freezing point is 49.2 C. Calculate the molar mass of the solute.
delta T = Kf*molality
delta T = normal freezing point of 1,4-dichlorobenzene - 49.2.
Kf is the freezing point constant for 1,4 dichlorobenzene. Substitute in the equatiohn and solve for m.
m = molslity = mols/kg solvent. You have kg solvent (0.040g) and you have m. Substitute and solvel for mols.
Then mols = grams solute/molar mass. You have mols and grams, substitute and solve for molar mass.