Molality Calculator
Determine the molality (moles of solute per kilogram of solvent) of a solution. Ideal for chemical thermodynamics since molality is temperature-independent.
Solution Parameters
Enter solute details and solvent mass.
Solution Molality (m)
* Temperature-independent concentration standard.
Expert Tip
Use molality rather than molarity for studies tracking properties across temperature changes (e.g. boiling point elevation, freezing point depression), since liquid volumes expand or contract with temperature, but masses do not.
Methodology & Equations
Molality Equation
Unlike molarity (which is moles per liter of solution), molality is defined relative to the mass of the pure solvent:
Comparison: Molality vs Molarity
- Molality (m): Solute moles per 1 kg solvent. Does not vary with temperature or pressure. Used in colligative property investigations.
- Molarity (M): Solute moles per 1 L solution. Dependent on volume, hence sensitive to thermal expansion. Used in general stoichiometry setups.
How to Calculate Molality of a Solution
Molality (m) is a concentration unit representing solute moles per kilogram of solvent. Unlike molarity, it is temperature-independent:
Find Solute Moles
Divide solute mass (g) by its molecular weight (g/mol): Moles = Mass / Molecular Weight.
Convert Solvent Mass to Kilograms
If the mass of solvent is in grams, divide by 1000 to convert to kg.
Compute Molality (mol/kg)
Divide moles of solute by kilograms of solvent: Molality = Moles / Solvent Mass (kg).
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Convert molar concentration back to required solute mass or solvent volume.
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Compute solution osmolarity based on solute molarity and dissociation characteristics.