What is the freezing point of a solution that contains 3.5 mol of the ionic solid BaCl2 dissolved in 500 grams of water?
dT = i*kf*m
i = 3 for BaC;2
Kf = 1.86
m = molality = mols/kg solvent
Substitute and solve for delta T.
Subtract delta T from zero C to find the new freezing point.