A 7.85 g sample of a compound with the empirical formula C5H4 is dissolved in 301 g of benzene. The freezing point of the solution is 1.05C below that of pure benzene. what are the molar mass and molecular formula of this compound?

Answer 1

delta T = Kf*m
You know delta T and Kf, solve for molality.
Then molality = mols/kg solvent. You know m and kg solvent, solve for mols.

Then mols = grams/molar mass. You know mols and grams, solve for molar mass.

The empirical formula is C5H4. Calculate the empirical formula mass.
empirical formula mass x n = molar mass.
The molecular formula then is
(emprical formula)_n