Molar concentration

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, [math]\displaystyle{ c_i }[/math] is defined as the amount of a constituent [math]\displaystyle{ n_i }[/math] (usually measured in moles – hence the name) divided by the volume of the mixture [math]\displaystyle{ V }[/math]:

[math]\displaystyle{ c_i = \frac {n_i}{V} }[/math]

The volume [math]\displaystyle{ V }[/math] in the definition [math]\displaystyle{ c_i = n_i/V }[/math] 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.

References

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