Freezing Point Depression and Concentration of Solute

As verified experimentally, for a dilute solution the freezing point depression ($\Delta T_f$) is directly proportional to the molality of the solution. Thus,

The proportionality constant $K_f$ is called the freezing point depression constant or cryoscopic constant.

If $m = 1$, then $\Delta T_f = K_f$. The cryoscopic constant thus is the depression in freezing point produced by a 1 molal solution of a nonvolatile solute. …