Calculate the mass percent of O present in sodium sulphate (Na₂SO₄)

The molar mass of sodium sulphate is 2(23) + 32 + 4(16) = 46 + 32 + 64 = 142 g/mol
Mass percentage = (Mass of oxygen / Mass of Na₂SO₄) × 100
The mass percentage of oxygen in sodium sulphate = (64 / 142) × 100 = 45.07