Molar concentration

Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solvent or solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the mole per liter (mol/L). A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M.

Definition

Molar concentration is defined as the amount of a constituent (usually measured in moles) divided by the volume of the mixture (usually measured in liters). The formula for calculating molar concentration is:

C = n/V

where C is the molar concentration in moles per liter (mol/L), n is the amount of substance in moles, and V is the volume of the solution in liters.

Units

The SI unit for molar concentration is mol/m^3. However, mol/L is a more commonly used unit and is equivalent to M (molar). Other units such as mmol/L (millimoles per liter), μmol/L (micromoles per liter), and nmol/L (nanomoles per liter) are also used, especially when dealing with low concentrations.

Applications

Molar concentration is widely used in chemistry for the preparation of solutions, in stoichiometry calculations, and in analytical chemistry for determining the concentration of analytes. It is fundamental in the study of reaction rates, chemical equilibrium, and osmotic pressure.

Calculating Molar Concentration

To calculate the molar concentration of a solution, one needs to know the amount of solute (in moles) and the volume of the solution (in liters). The amount of solute can be determined by weighing the substance (using its molar mass) or by stoichiometric calculations from a preceding reaction.

Examples

1. Preparing a 1 M solution of NaCl involves dissolving 58.44 g of NaCl (the molar mass of NaCl) in enough water to make 1 liter of solution. 2. If 0.5 moles of glucose (C6H12O6) is dissolved in 0.5 liters of water, the molar concentration of the solution is 1 M (0.5 moles / 0.5 liters).

Limitations

Molar concentration can change with temperature, as the volume of the solution expands or contracts with temperature fluctuations. Therefore, it is important to specify the temperature at which the molarity is measured.

See Also

• Molality
• Normality (chemistry)
• Mass concentration (chemistry)
• Volume concentration