Question

Kjeldahl's method was used for the estimation of nitrogen in an organic compound. The ammonia evolved from $0.55 g$ of the compound neutralised $12.5\, mL$ of $1 \,M\, H _{2} SO _{4}$ solution. The percentage of nitrogen in the compound is ______(Nearest integer)

Answer 1

Meq of $H _{2} SO _{4}$ used by $NH _{3}=12.5 \times 1 \times 2=25$
$\%$ of $N$ in the compound $=\frac{25 \times 10^{-3} \times 14 \times 100}{0.55}=63.6$ or
Meq. of $H _{2} SO _{4}=$ Meq. of $NH _{3}$
12. $5 \times 1 \times 2=25$ meq. of $NH _{3}$
$=25$ millimoles of $NH _{3}$
So Millimoles of ' $N$ ' $=25$
Moles of ' $N ^{\prime}=25 \times 10^{-3}$
wt. of $N =14 \times 25 \times 10^{-3}$
$\% N =\frac{14 \times 25 \times 10^{-3}}{0.55} \times 100$
$=63.66$
$\approx 64 \%$