Freezing point depression calculator
Freezing point falls in proportion to molality, which is why salt clears ice and why it stops working when it gets cold enough.
mol/kg
K kg/mol
Water: 1.86. Benzene: 5.12. Camphor: 40.
Particles per formula unit: 1 for sugar, 2 for NaCl, 3 for CaCl2.
New freezing point
-3.720°C
- Depression
- 3.7200 K
Show the working
- Molality = 1
- Cryoscopic constant = 1.86
- Van't Hoff factor = 2
- Normal freezing point = 0
- Depression = 2 * 1.86 * 1 = 3.72
- New freezing point = 0 - 3.72 = -3.72
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- delta T = i x Kf x molality
- new freezing point = normal freezing point - delta T
Saturated brine freezes at about -21 degrees Celsius, which is why rock salt stops being useful below roughly -10.