Cryoscopic Constant
The freezing point depression produced by a one-molal solution of a non-electrolyte in a given solvent.
Formula / equation
K_f = RT_f²M / ΔH_fus
Unit
K·kg/mol
In depth
Like its boiling-point counterpart, K_f depends only on the solvent and is largest for solvents with a low enthalpy of fusion. Camphor's exceptionally large value made Rast's method a standard microtechnique for organic molar mass determination.
Examples in the real world
Water has K_f = 1.86 K·kg/mol, benzene 5.12, and camphor an extraordinary 40 K·kg/mol.