We’re being asked to determine the solution will have the lowest freezing point.

Recall that the freezing point of a solution is *lower* than that of the pure solvent and the *change in freezing point (ΔT*_{f}) is given by:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{f}}}{\mathbf{=}}{{\mathbf{T}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{pure}\mathbf{}\mathbf{solvent}}{\mathbf{-}}{{\mathbf{T}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{solution}}}$

The *change in freezing point* is also related to the molality of the solution:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{f}}}{\mathbf{=}}{{\mathbf{imK}}}_{{\mathbf{f}}}}$

where:

**i** = van’t Hoff factor

**m** = molality of the solution (in m or mol/kg)

**K**_{f} = freezing point depression constant (in ˚C/m)

The solution with the highest change in freezing point (ΔT_{f}) will be the solution with the lowest freezing point.