1.2 Calculate the mass per cent of different elements present in sodium sulphate (Na2SO4).

The molecular formula of sodium sulfate is Na2SO4.
Molar mass of Na2SO4 = [(2 × 23.0) + (32.066) + 4 (16.00)]
= 142.066 g

The mass percent of an element = Mass of thet element in the compoundMolar mass of the compound × 100
 The mass percent of sodium:

= 46.0 g142.066 × 100
= 32.379
= 32.4%

The mass percent of sulphur:

= 32.066 g142.066 × 100
= 22.57
= 22.6%

The mass percent of oxygen:

= 64.0 g142.066 × 100
= 45.049
= 45.05%