A sample of 0.5 g of an organic compound was treated according to Kjeldahl's method. The ammonia evo

Question

A sample of 0.5 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M solution of $\mathrm{H}_{2} \mathrm{SO}_{4}$. The residual acid required 60 mL of 0.5 M solution of NaOH . The percentage of nitrogen in the organic compound is\

Professor PC Thomas Classes · Answer

$60 \mathrm{~mL} 0.5 \mathrm{~m} \mathrm{NaOH} \equiv 30 \mathrm{~mL} 0.5 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ Initial volume of $0.5 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{~V}_{1}=50 \mathrm{~mL}$ Volume of $0.5 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ left behind, $$ \mathrm{V}_{2}=30 \mathrm{~mL} $$ Volume of $0.5 \mathrm{M} \mathrm{NH}_{3}$ solution reacted $$ =50-30=20 \mathrm{~mL} $$ Volume of $0.5 \mathrm{M} \mathrm{NH}_{3}$ formed $=2 	imes 20$ $$ =40 \mathrm{~mL} $$ Percentage of nitrogen\ $=\frac{1.4 \mathrm{VN}}{\mathrm{w}}=\frac{1.4 	imes 40 	imes 0.5}{0.5}=56 \%$\