Calculate the mass percentage of different elements present in sodium sulfate $(Na_2SO_4)$.

The molar mass of $Na_2SO_4$ is calculated as follows:
$Molar \ mass = (2 \times 22.99 \ g/mol) + 32.06 \ g/mol + (4 \times 16.00 \ g/mol) = 142.04 \ g/mol$
Mass percentage of $Na = \frac{2 \times 22.99}{142.04} \times 100 = 32.37\%$
Mass percentage of $S = \frac{32.06}{142.04} \times 100 = 22.57\%$
Mass percentage of $O = \frac{4 \times 16.00}{142.04} \times 100 = 45.06\%$