Molar concentration

measure of the concentration of a solute in a solution, or of any chemical species, in terms of amount of substance in a given volume; most commonly expressed in units of moles of solute per litre of solution

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

In chemistry, the molar concentration, is defined as the amount of a constituent (usually measured in moles – hence the name) divided by the volume of the mixture :[1]

The volume in the definition 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.


  1. International Union of Pure and Applied Chemistry. Amount concentration, c. Compendium of chemical terminology, internet edition. [1]