What does molarity mean?
Molarity is a unit of concentration used in chemistry to describe how much solute is present in a given volume of solution. It is calculated by dividing the number of moles of solute by the volume of solution in litres, and is commonly written with the unit mol/L or simply M. A 1 M solution contains one mole of solute per litre, while a 0.1 M solution contains one tenth of a mole per litre. The measure is useful in laboratory preparation, chemical reactions, biochemistry, and pharmacology, where accurate concentrations are important. Molarity depends on the solution's final volume, so dilution changes its value. It differs from molality, which compares the amount of solute with the mass of solvent rather than the volume of the complete solution.
nounMolarity is a measure of the concentration of a solute in a solution, expressed as the number of moles of solute per litre of solution. The unit of molarity is moles per litre, abbreviated mol/L or M.
- A chemical concentration measurement equal to the number of moles of solute per litre of solution.
"The molarity of the sodium hydroxide solution was reduced by diluting it with water."
"Students calculated the molarity of each solution before beginning the titration."
"The drug was administered at a carefully controlled molarity."
Used when referring to the molarities of multiple solutions or to several concentration values.
"The table compares the molarities of the samples at different stages of the experiment."
A one-molar solution contains exactly one mole of solute in every litre of solution, making molarity a direct link between chemistry calculations and laboratory preparation.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does molarity come from?
Molarity was formed in the 19th century from the adjective molar, meaning relating to a mole or a molar mass, together with the suffix -ity. Its underlying Latin root, moles, referred to a mass or quantity and gave rise to modern scientific terms such as mole and molecular. The development of modern chemical theory and the adoption of the mole as a unit made molarity a practical measure of solution concentration.
Related word forms
How molarity is actually used
Molarity is primarily used in chemistry, biochemistry, pharmacology, and related scientific fields. In everyday discussion, it is usually abbreviated as M, as in 0.1 M. It should not be confused with molality, which uses the mass of solvent rather than the volume of solution.
Easily confused with molarity
Molarity measures moles of solute per litre of solution, whereas molality measures moles of solute per kilogram of solvent.