Freezing Point Depression Calculator

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Forward computes ΔTf from molality. Reverse modes work backwards from a measured depression.
Choosing a preset auto-fills Kf and the pure solvent freezing point.
The molal freezing-point-depression constant for the chosen solvent. Water = 1.86, benzene = 5.12, cyclohexane = 20.0.
°C·kg/mol
The normal freezing point of the pure solvent. 0 °C for water.
°C
For non-electrolytes leave this off (i = 1). Turn on to set i for salts and electrolytes.
Moles of solute per kilogram of solvent (not per litre of solution).
mol/kg
Freezing point depression (ΔTf)
1.86°C
Solution freezing point-1.86°C
1.86 °C
Small depression<2Moderate depression2-5Large depression5+

ΔTf = 1.86 °C, solution freezes near -1.86 °C.

  • The solution freezes about 1.86 °C lower than the pure solvent.
  • Freezing point depression is colligative: it depends only on particle count, not chemical identity.
  • Practical example: road salt (NaCl, i ~ 2) depresses water by about 3.72 °C per mol/kg.

Next stepThe same dissolved particles also raise the boiling point. Try the boiling point elevation calculator (ΔTb = i·Kb·m).

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