• # question_answer 10) Calculate the percentage composition of each element in Sodium sulphate $N{{a}_{2}}S{{O}_{4}}.$

Molecular mass of $N{{a}_{2}}S{{O}_{4}}=23\times 2+32+16\times 4$ = 46 + 32 + 64 $=142\text{ }amu$ $\text{ }\!\!%\!\!\text{ Sodium =}\frac{\text{Mass of Sodium}}{\text{Mass}\,\text{of}\,\text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}}\times 100$ $=\frac{46}{142}\times 100=324$ $\text{ }\!\!%\!\!\text{ Sulphur =}\frac{\text{ }\!\!~\!\!\text{ Mass of Sulphur }\!\!~\!\!\text{ }}{\text{Mass}\,\text{of}\,\text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\text{ }\!\!~\!\!\text{ }}\text{ }\!\!\times\!\!\text{ 100}$ $=\frac{32}{142}\times 100=22.59$ % Oxygen $=100-(32.4+22.5)=45$