Question

In the Kjedahl's method for estimation of nitrogen present in soil sample, ammonia evolved from 0.75 g of sample neutralized 10 ml. of $1M{H}_{2}S{O}_4$. The percentage of nitrogen in the soil is:

• A. $37.33$
• B. $35.33$
• C. $445.33$
• D. $43.33$

Answer 1

The correct option is A $37.33$

$\text{10 ml}$ of $1M{H}_{2}S{O}_4$ corresponds to $\text{10 mmol}$

It will neutralize $\text{20 mmol}$ of $N{H}_3$.

$\text{Weight of N}=\frac{14\times 20}{1000}g=0.280g$.

Thus $0.75$ of sample of organic compound contains $0.280g$ of nitrogen.

The percentage of nitrogen in the organic sample is $\frac{0.280}{0.75}\times 100=37.33$%