Freezing Point Depression

Calculate the freezing point depression of a solution from the cryoscopic constant, molality, and van't Hoff factor.

Inputs

Cryoscopic Constant (Kf)

°C/m

Molality

mol/kg

van't Hoff Factor (i)

Tab to move between fields

Results

Freezing Point Depression (ΔTf)

1.86 °C

New Freezing Point

-1.86 °C

Effective Particle Molality1 mol/kg

How to Use This Calculator

Enter the cryoscopic constant (Kf) for your solvent — water is 1.86 °C·kg/mol.
Set molality (mol/kg) and van't Hoff factor (i).
Enter the normal freezing point of the pure solvent.
Review Freezing Point Depression (ΔTf) and New Freezing Point.

How the result changes with Cryoscopic Constant (Kf)

Cryoscopic Constant (Kf)	Freezing Point Depression (ΔTf)	New Freezing Point
10	10 °C	-10 °C
35	35 °C	-35 °C
65	65 °C	-65 °C
90	90 °C	-90 °C

What each input means

Cryoscopic Constant (Kf): Freezing point depression constant for the solvent (water Kf = 1.86 °C·kg/mol)
Molality: Moles of solute per kilogram of solvent
van't Hoff Factor (i): Number of particles per formula unit in solution (NaCl = 2, CaCl₂ = 3, sugar = 1)
Normal Freezing Point: Freezing point of the pure solvent (water = 0 °C)

How this is calculated

Formula

ΔTf = i × Kf × m

Worked example, using the default values

Identify Input Parameters
4 parameters
Cryoscopic Constant (Kf) = 1.86, Molality = 1, van't Hoff Factor (i) = 1, Normal Freezing Point = 0 = 4 input(s) provided
Calculate Freezing Point Depression
Freezing Point Depression
1.86 = 1.86
Calculate New Freezing Point
New Freezing Point
-1.86 = -1.86
Calculate Effective Particle Molality
Effective Particle Molality
1 = 1

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