The depression in the freezing point of a solution is defined as the difference between the freezing points of a pure solvent and that of the solution.
If T0 and T are the respective freezing points of a pure solvent and a solution, then the depression in the freezing point ΔTf is given by,
ΔTf = T0 – T (T < T0)
The depression in the freezing point (ΔTf) is a colligative property.
