Question

Calculate the mass per cent of different elements present in sodium sulphate $(\text{Na}_2\text{SO}_4)$.

Answer 1

The molecular formula of sodium sulphate is $(\text{Na}_2\text{SO}_4)$.
Molar mass of $(\text{Na}_2\text{SO}_4)$= [(2 × 23.0) + (32.066) + 4 (16.00)]
= 142.066 g
Mass percent of an element $= \frac{\text{Mass of that element in the compound} }{ \text{Molar mass of the compound}} × 100$
∴ Mass percent of sodium:
$= \frac{46.0 g }{ 142.066 g} × 100$
= 32.379
= 32.4 %
Mass percent of sulphur:
$= \frac{32.066 g }{ 142.066 g} × 100$
= 22.57
= 22.6 %
Mass percent of oxygen:
$= \frac{64.0 g }{ 142.066g} × 100$
= 45.049
45.05%