Question

A sample of 0.50 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 ml of 0.5 M $H_{2}S{O}_4$. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralization. The percentage composition of nitrogen in the compound is :

• A. 56%
• B. 60%
• C. 62%
• D. 58%

Answer 1

Answer: (A)

56%

From Kjeldahl's method, we know that pPercentage of nitrogen in the sample =
$\frac{(1.4\times Normalityofacid\times volumeofacidusedforneutralisation)}{\left(massofcompoundtaken\right)}=\frac{1.4\times 1\times 20}{0.5}=56$ %

(As volume of acid used with $NaOH$ is $30$ ml so only $20$ ml is used for ammonia)