Normality:It is defines as the number of gram equivalents of solute present per litre of solution. It is denoted by ‘N’.Normality (N) = Number of gram equivalents of solute/Number of litres of the solutionor Normality × Number of llitres of the solution= Number of gram equivalents of the soluteLet w_{A}gram of the solute of equivalent mass E_{A}be present in V litres of the solution, then,Normality = w_{A}/E_{A}/V = w_{A}/E_{A}×VNormality × Equivalent mass – w_{A}/V= Strength of the solution g/L.Solutions are expressed as1 N, 2 N, N/2, N/10, N/100, N/1000 etc.1N = Normal= One gram equivalent of the solute per litre of solution= Normality is 1N/2 = Seminormal= 0.5 g equivalent of the solute per litre of solution= Normality is 0.5N/10 = Decinormal= 0.1 g equivalent of the solute per litre of solution= Normality is 0.1N/100 = Centinormal= 0.01 g equivalent of the solute per litre of solution= Normality is 0.01N/1000 = Millinormal= 0.001 g equivalent of the solute per litre of solution= Normality is 0.001

Relationship between normality and molarity:We know thatMolarity × Molecular mass = Strength of solution (g/L)Similarly,Normality × Equivalent mass = Normality of the solution (g/L)Hence,Molarity × Molecular mass = Normality × Equivalent massor Normality/Molarity = Molecular mass/Equivalent mass = nSo Normality = n × Molarity[Normailty (second method): Let ‘d’ is the density of solution in g/mL and x is the percentage of the solute by mass.Then,N = x×d×10/Equivalent mass of solute

Formality:

It is the number of formula mass in grams present per litre of solution. In case formula mass is equal to molecular mass, formality is equal to molarity. Like molarity and normality, the formality is also dependent on temperature. It is used for ionic compounds in which there is no existence of molecule. Mole of ionic compounds is called formole and molarity as formality.