Question

For the estimation of nitrogen, $1.4$ g of an organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in 60 mL of $\frac{M}{10}$ sulphuric acid. The unreacted acid required 20 mL of $\frac{M}{10}$sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is:

Answer 1

In Kjeldahl method,

% $N=\frac{1.4NV}{W}$

Weight of organic compound= $1.4g$

Given $\frac{M}{10}{H}_{2}S{O}_4=\frac{1}{5}\times 60=12M_{eq}$

$\frac{M}{10}NaOH=\frac{1}{10}\times 20=2Meq$

Hence used $H_{2}S{O}_4$ against $N{H}_3=12-2=10M_{eq}$

$\therefore$ % of $N=\frac{1.4\times 10}{1.4}=10$% .