Question

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

Answer 1

Solution: From formula

Mass % of an element = Molar mass of component/Molar mass of compound ×100

The molecular formula of compound (Na₂SO₄) is 
= [(2 × 22.99) + (32.06) + 4 (16.00)]
= 142.04 g 
Molar mass of 2Na  =  2 × 22.99  = 45.98 amu 
Molar mass of 4O  = 4 × 16.00  = 64.00 amu 
Now put the values in above formula 
Mass percent of sodium  =  45.98 ×100 /142.04 = 32.37% 
Mass percent of sulphur  = 32.06 ×100 /142.04 = 22.57% 
Mass percent of oxygen  = 64.00 ×100 /142.04 = 45.06%