Molar concentration

Molar concentration, or molarity, or simply concentration, is a term in chemistry, and its physical chemistry branch. It measures the concentration of a solution or mixture.

In chemistry, the molar concentration, ${\displaystyle c_{i}}$ is defined as the amount of a constituent ${\displaystyle n_{i}}$ (usually measured in moles – hence the name) divided by the volume of the mixture ${\displaystyle V}$:^[1]

${\displaystyle c_{i}={\frac {n_{i}}{V}}}$

The volume ${\displaystyle V}$ in the definition ${\displaystyle c_{i}=n_{i}/V}$ refers to the volume of the solution, not the volume of the solvent. One litre of a solution usually contains either slightly more or slightly less than 1 litre of solvent because when a substance dissolves in a solvent it causes volume of liquid to increase or decrease.

The reciprocal quantity represents the dilution (volume) which can appear in Ostwald's law of dilution.