Question

$0.2\text{g}$ of an organic compound was analysed by Kjeldahl’s method. The ammonia evolved was absorbed in $60\text{ml}$ of $N/5H_{2}S{O}_4$. Unused acid required $40\text{ml}$ of $N/10NaOH$ for complete neutralization. Find the percentage of nitrogen in the compound.

Answer 1

Mass of organic compound $=0.2\text{g}$
Unused acid required $=40\text{ml}$ of $\frac{N}{10}NaOH$
$40\text{ml}\frac{N}{10}NaOH\equiv 20\text{ml}\frac{N}{5}{H}_{2}S{O}_4$
Acid used for absorption of ammonia
$=(60-20)\text{ml}{H}_{2}S{O}_4=40\text{ml}\frac{N}{5}{H}_{2}S{O}_4$
Percentage of nitrogen $=\frac{14\times N_1\times V}{W\times 1000}\times 100=\frac{1.4\times \frac{1}{5}\times 40}{0.2}=\frac{1.4\times 40}{0.2\times 5}=56$