Molality Calculator

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Choose how you want to enter the solute amount.
The amount of dissolved substance in moles (mass of solute divided by its molar mass).
mol
Mass of the solvent only, not the total solution.
Cryoscopic (Kf) and ebullioscopic (Kb) constants for the chosen solvent are applied automatically.
Number of particles a formula unit dissociates into: 1 for non-electrolytes (glucose), 2 for NaCl, 3 for CaCl2, etc.
MolalityModerate
1mol/kg

Moles of solute per kilogram of solvent.

Moles of solute1mol
Freezing-point depression1.853K
Boiling-point elevation0.512K
1 mol/kg
Very dilute<0.1Dilute0.1-1Moderate1-5Concentrated5-10Very conc.10+

Molality: 1 mol/kg in Water.

  • Molality divides by the mass of the solvent, so it never changes with temperature, unlike molarity, which uses volume.
  • The denominator is solvent mass alone, not the combined mass of solute and solvent.
  • For Water with i = 1: the freezing point drops by 1.853 K and the boiling point rises by 0.512 K.

Next stepStudying colligative properties? The freezing-point depression and boiling-point elevation are already computed below. For ionic solutes, increase the van 't Hoff factor (i = 2 for NaCl, 3 for CaCl2).

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