Question

The percentage of N in 66 g pure $(N{H}_4{)}_{2}S{O}_4$ sample is :

• A. $32$
• B. $28$
• C. $21$
• D. none of the above

Answer 1

Answer: (C)

$21$

The atomic masses of N, H, S and O are 14 g/mol, 1 g/mol, 32 g/mol and 16 g/mol respectively.
The molar mass of $(N{H}_4{)}_{2}S{O}_4=2(14+4\left(1\right))+32+4(16)=132$ g/mol.
The percent of nitrogen $=100\times \frac{2\times 14}{132}=21$ %.