Question

In the Kjeldahl’s method for estimation of nitrogen present
in a soil sample, ammonia evolved from 0.75 g of sample
neutralized 10 mL of 1 M H₂SO₄. The percentage of nitrogen
in the soil is : [2014]
(a) 37.33 (b) 45.33
(c) 35.33 (d) 43.33

Answer 1

Explanation:

The percentage of nitrogen

in the soil is 35.33 percent

Answer 2

(a) 37.33

Explanation:

H2SO4 + 2NH3 → (NH4)2SO4  

10ml of 1M H2SO4 = 10 mmol

NH3 consumed = 20 mmol.

So the acid used for the absorption of ammonia = 20-10 = 10 ml

That would be 10ml of 2N or 1M solution of sulphuric acid.

Percentage of nitrogen = 1.4 * N * V / W

= 1.4 * 2 * 10 / 0.75  

= 37.33%

Option A is the answer.