Question

0.4422 gm. of an organic substance was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 cc of 1N $H_{2}SO_{4}$. The residual acid required 65.5 cc of N/2 alkaline solution. Find the percentage of nitrogen in the compound.

Answer 1

grams of nitrogen/grams of sample x 100% = percentage of nitrogen in the unknown sample

Answer 2

Kjeldahl method is used in quantitative determination of nitrogen present in inorganic compounds like ammonia and ammonium.

Equivalent weight of the acid taken = $\quad 50\quad \times \quad 1\quad =\quad 50$

Equivalent weight of the acid neutralized by alkaline solution =$\quad 65.5\quad \times \quad \frac { 1 }{ 2 } \quad =\quad 32.75$

Equivalent weight of the acid neutralized by ammonia =$\quad 50\quad -\quad 32.75\quad =\quad 17.25$

$Percentage\quad of\quad nitrogen=\quad \frac { 1.4\quad \times \quad N\quad \times \quad V }{ Weight\quad of\quad the\quad substance } \quad \\ \\=\quad \frac { 1.4\quad \times \quad 17.25 }{ 0.4422 } \quad$

Percentage of nitrogen =$\quad 54.61%\quad$