Molarity

Definition

Concentration as moles of solute per liter of solution: the most common concentration unit in chemistry labs.

$M = \frac{n}{V}$

Symbol: $M$ · Unit: mol/L

Technical definition

Molarity (M) is moles of solute per liter of solution. It is temperature-dependent because solution volume expands with temperature, and it is the standard concentration unit for stoichiometry and titrations.

Example

Dissolving 58.44 g of NaCl (1 mol) in water and diluting to exactly 1.00 L gives a 1.00 M solution.

Common confusion

Molarity uses liters of SOLUTION, not solvent. Dissolving 1 mol of salt in 1 L of water gives slightly more than 1 L of solution, so the molarity is slightly less than 1 M.