Molarity

Molarity, denoted M, is the single most widely used way of expressing solution concentration in a laboratory. It is defined as the number of moles of solute dissolved in exactly one litre of the solution: $\text{Molarity } (M) = \dfrac{\text{no. of moles of solute}}{\text{volume of solution in litres}}$. Because molarity is defined per unit VOLUME of solution, and the volume that a given mass of solution occupies changes with temperature (liquids expand slightly on heating and contract on cooling), the molarity of a solution is itself dependent on temperature, even though the actual amount of dissolved solute has not changed — only the volume it is dissolved in has. This temperature sensitivity is an important practical limi …