Why use molality instead of molarity?

Molality doesn't change with temperature (since mass doesn't change), while molarity does (since volume changes slightly with temperature), making molality preferred for precise thermodynamic calculations.

Molality Calculator

Molality expresses concentration as moles of solute per kilogram of solvent, unlike molarity which uses volume of solution.

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Molality: 1.25 mol/kg

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Formula

Molality = Moles of Solute / kg of Solvent

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Solution Concentration: Five Ways to Express the Same Idea

Mass percent, molality, parts per million, percent composition, and dilution factor — five different units for describing how concentrated a solution is.

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