The molar mass of a non-dissociated, non-volatile compound is to be determined by dissolving 5.00 g of the compound into 50.0 g of benzene. The freezing point of benzene was lowered by 2.5 degrees C. The freezing point depression constant (Kf) for benzene is 5.0 degree C/molal. What is the molar mass of this compound?
delta T = Kf m
delta T is given as 2.5o C
Kf = 5.0 C/molal
solve for m = molality.
Then m = # mols/kg solvent and mols = grams/molar mass.
Post your work if you get stuck.
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