Difference Between Normality and Molarity

Normality vs Molarity
 

Molarity and normality are two important and commonly used phenomena in chemistry. Both terms are used to indicate quantitative measurement of a substance. If you want to determine the amount of copper ions in a solution, it can be given as a concentration measurement. All most all the chemical calculations are using concentration measurements to draw conclusions about the mixture. To determine the concentration, we need to have a mixture of components. To calculate the concentration of each component, the relative amounts dissolved in the solution have to be known. Concentration is a wider term used, and molarity and normality are types of concentration measurement.

Normality

As stated above normality is another way of indicating concentration. “N” is the symbol used to denote normality. Normality is given as equivalents per liter. An equivalent is the number of moles of reactive units in a compound. Eq/L and mol/L are the units used to indicate normality. For example, one mole of hydrogen chloride gives one mole of hydrogen ions and one mole of chloride ions into the solution. One mole of hydrogen ions is equal to one equivalent of hydrogen ions. Therefore, 1M HCl is the same as 1N HCL, but when we take sulfuric acid, 1 mole of sulfuric acids gives 2 moles of hydrogen ions into the solution. Therefore, normality of hydrogen ions will be 2N for a sulfuric acid solution. For further understanding of normality, we’ll take a calcium chloride solution. For chloride ions, the normality is 2 N because one mole of calcium chloride yields two moles of chloride ions. For calcium, the valency is +2. So it is like calcium can take place of two hydrogen ions. Therefore, its normality is also 2.

Molarity

Molarity is also known as molar concentration. This is the ratio between the number of moles of a substance in one volume of a solvent. Conventionally, the solvent volume is given in cubic meters. However, for our convenience we often use liters or cubic decimeters. Therefore, the unit of the molarity is mol per liter/ cubic decimeter (mol l-1, mol dm-3). The unit is also indicated as M. For example, a solution of 1 mol of sodium chloride dissolved in water has a molarity of 1 M. Molarity is the most commonly used method of concentration. For example, it is used in the calculation of pH, dissociation constants/ equilibrium constants, etc. Conversion of a mass of a given solute to its molar number has to be done in order to give the molar concentration and, to do this, mass is divided by the molecular weight of the solute. For example, if want to prepare a 1 M of potassium sulfate solution, 174.26 g mol-1 (1 mol) of potassium sulfate should be dissolved in one liter of water.

 

What is the difference between Normality and Molarity?

• Normality is given as equivalents per liter. Molarity is given as the number of moles per liter.

• Normality provides information about the number of reactive units in one liter of a solution, whereas molarity provides information about the number of molecules in one liter of solution.

• Normality of a solution can be given by molar concentration divided by equivalence factor.