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what is molality?

Molality is the number of moles of solute per kilogram of solvent. It is important the mass of solvent is used and not the mass of the solution. Solutions labeled with molal concentration are denoted with a lower case m. A 1.0 m solution contains 1 mole of solute per kilogram of solvent.

For aqueous solutions (solutions where water is the solvent) near room temperature, the difference between molar and molal solutions is negligible. This is because around room temperature, water has a density of 1 kg/L. This means the "per L" of molarity is equal to the "per kg" of molality.


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