Question

A sample of 0.50 gram of an organic compound was treated according to kjeldahl method the ammonia evolved was absorbed in 50 ml 0.5 molarity of h2so4 the residual acid required 60 ml of 0.5 m solution of naoh for neutralization find the percentage composition of nitrogen in the compound

Answer 1

Mass of organic compound = 0.50 g

Initial volume of acid = 50 mL

Molarity of acid = 0.5 M

Volume of NaOH of 0.5 M molarity required for neutralization of residual acid = 60 mL

= 30 mL of 0.5 M H2SO4

Volume of H2SO4 (0.5 M) consumed = (50 - 30) = 20

20 ml of 0.5 M H2SO4== 40 mL of 0.5 M NH3 or 20 ml of 1 M NH3

1000 mL of 1 M NH3 contains 14 g Nitrogen (1 mol of N2)

20 mL of 1 M NH3 contains 17*20/1000g Nitrogen

0.5g of organic compound contains 14*20/1000g N

100 g of organic compound contains =14*20*100/1000*0.5g=56% of N2