Question

The ammonia evolved from 2g of a compound in Kjeldahl's estimation of nitrogen neutralizes 10 mL of 2 M $H_{2}S{O}_4$ solution. The weight percentage of nitrogen in the compound is

• A. 28
• B. 14
• C. 56
• D. 7

Answer 1

The correct option is A

28

$2N{H}_2+H_{2}S{O}_4\stackrel{}{\to }(N{H}_4{)}_{2}S{O}_4$
10ml
2ml
millimole of $H_{2}S{O}_4=\frac{\text{mmol of}N{H}_3}{2}=20$
Mmol $N{H}_3$=mmol of N=40
$=\frac{40\times 14}{1000}=\frac{560}{1000}=0.56g$
$W_n$
% of N$=\frac{0.56}{2}\times 100=28$