Molecular mass of sodium sulphate (Na2SO4) is 142 g mol.
The elements present in sodium sulphate are sodium, sulphur and oxygen.
Mass of Sodium : 23 × 2 = 46 g
Mass of Sulphur : 32 × 1 = 32 g
Mass of Oxygen : 16 × 4 = 64 g
Mass percentage of sodium = \(\frac{32}{142}\) × 100
= 32.38 or 32.4%
Mass percentage of sulphur = \(\frac{32}{142}\) × 100
= 22.57 or 22.6
Mass percentage of oxygen = \(\frac{64}{142}\) × 100 .
= 45.05%