devarshi-dt-logo

Question:

In the Kjedahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75g of sample neutralized 10ml of 1M H2SO4. The percentage of nitrogen in the soil is:

445.33

35.33

43.33

37.33

Solution:

10 ml of 1M H2SO4 corresponds to 10 mmol.
It will neutralize 20 mmol of NH3.
Weight of N = 14 × 20/1000 g = 0.280 g.
Thus 0.75 g of sample of organic compound contains 0.280 g of nitrogen.
The percentage of nitrogen in the organic sample is 0.280/0.75 × 100 = 37.33