Question

At home, you dissolve 26.0 g of AlCl3 in 1.5 kg of water. What is the freezing point of this solution? (Normal f.p = 0.0 C, Kf= 1.86 C kg/mol)

Answer 1

mols AlCl3 = grams/molar mass. You know molar mass and grams, solve for mols.

Then m = molality = mols/kg solvent. You know kg solvent and mols, solve for m.

Then delta T = i*Kf*m
You know Kf and m; i for AlCl3 is 4. Solve for delta T.

Then subtract delta T from the normal freezing point to obtain the new freezing point.