Molality Calculator
Calculate molality (m) from moles of solute and mass of solvent in kilograms.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Enter the number of moles of solute and the mass of the solvent in kilograms. The calculator divides moles by mass to give molality in mol/kg. Remember that molality uses the mass of the solvent alone, not the total solution mass.
About the Molality Calculator
Molality measures the concentration of a solution as moles of solute per kilogram of solvent. Unlike molarity, molality is independent of temperature because mass does not change with temperature. This makes it the preferred concentration unit for colligative property calculations like boiling point elevation and freezing point depression.
Frequently Asked Questions
When should I use molality instead of molarity?
Use molality when temperature changes are involved, such as in colligative property calculations (boiling point elevation, freezing point depression). Molality does not change with temperature because it is based on mass, not volume.
How do I convert molality to molarity?
You need the density of the solution. Molarity = (molality x density) / (1 + molality x molar_mass_solute / 1000). This conversion depends on knowing the solution density.
What are the units of molality?
Molality is expressed in moles per kilogram of solvent (mol/kg), abbreviated as m. Unlike molarity, molality uses the mass of the solvent only, not the total solution volume.