molarnost

Molarity, or molarnost in some languages, is a measure of solute concentration defined as the amount of substance per volume of solution. The symbol M denotes molarity; its unit is moles per liter (mol/L).

The molarity is calculated as M = n / V, where n is the number of moles of solute and V is the total volume of the solution in liters. The volume must be the final volume after dissolution, not just the solvent volume. Molarity depends on temperature because liquids expand with heat and contract with cooling.

Molarity is widely used in chemical calculations and stoichiometry, but care is needed because mixing or dissolution can change the volume. For precise work, volumetric glassware (volumetric flasks) are used to prepare solutions to a known final volume.

Related concepts include molality (m, moles per kilogram of solvent), normality (N, equivalents per liter), and mole fraction. In many contexts, molarity is the practical concentration measure, especially for reactions in solution.

Example: To make 1000 mL of a 0.500 M NaCl solution, dissolve 0.500 moles of NaCl in enough water to reach a final volume of 1.000 L.