Molality
The concentration of a solution expressed as moles of solute per kilogram of solvent.
Formula / equation
m = n / mass of solvent (kg)
Unit
mol/kg
In depth
Because it is defined by mass rather than volume, molality does not change with temperature, which makes it the correct unit for colligative property calculations where wide temperature ranges are involved. In dilute aqueous solution its numerical value is close to the molarity.
Examples in the real world
One mole of glucose in 1.00 kg of water is 1.00 m; antifreeze concentrations are quoted in molality for freezing-point work.