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 ${\mathrm{H}}_2{\mathrm{SO}}_4$. The percentage of nitrogen in the soil is

According to law of equivalance,
10 ml, 1 M H₂SO₄ = 20 ml , 1 M NH₃
Therefore, weight of 'N' in one mole of NH₃ = 14 g
20 x 10^–3 mole NH₃ means 20 x 10^–3 x 14g
sample of organic compound = 0.75 g
Percentage of nitrogen in a organic compound $=\frac{14\times 20\times {10}^{-3}}{0.75}\times 100=37.33\mathrm{\%}$