What are Molarity, Molality and Normality. Explain with Example

Answer : Molarity

Molarity is generally denoted by (M), and It is defined as the ratio of the number of moles present in a solute to the solution per litre.

Molarity = moles of solute / solution in litres

Example = Molecular mass of sulphuric acid is equal to 98. Now, if 98g of sulphuric acid is present in 1 litre of solution, it is a 1 molar mixture of sulphuric acid, and hence the molarity will equal 1. 

Molality

It is generally denoted by (m) and is defined as the ratio of the number of moles in a given solute to solvent, measured in kg.

m = moles of solute / solvent in kg

Example = If 98g of sulphuric acid is present in 1 kg of water, it will hold a molal solution equal to 1, and the molality will be equal to 1.

Normality

Normality is generally donated by (N) and is defined as the number of cognitions or equivalents per litre of a solution. 

N = Number of cognitions or equivalent / solution of 1 litre

Example = A 1N HCl solution = A 1Molar HCl solution because only I mole of H⁺ is constituted per mole of Hydrochloric acid (HCl).

Nevertheless, with sulphuric acid H₂SO₄, 2 moles of H⁺ are created per mole of acrid or acid; hence, 1 Molar H₂SO₄ = 2N H₂SO₄.