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Colligative properties depend on how many dissolved particles there are, not what they are. Freezing point falls by i.Kf.m and boiling point rises by i.Kb.m, where i counts the particles each formula unit releases. One molal sodium chloride (i = 2) in water depresses freezing by 3.72 K and raises boiling by about 1.02 K.
Freezing point depression
dTf = i x Kf x molality
Boiling point elevation
dTb = i x Kb x molality
The number of particles a formula unit produces in solution: 1 for sugar, 2 for NaCl, 3 for CaCl2. Real values fall slightly short because of ion pairing.
Because molality uses solvent mass, which does not change with temperature. Molarity would drift as the solution expanded or contracted.