A sample of 0.50 g of an organic compound was treated according to Kjeldahl’s method. The ammonia evolved was absorbed in 50 mL of 0.5 M $$H_2SO_4$$. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

Asked by Pragya Singh | 1 year ago |  80

##### Solution :-

Given that, total mass of organic compound = 0.50 g

60 mL of 0.5 M solution of NaOH was required by residual acid for neutralisation.

60 mL of 0.5 M NaOH solution = $$\dfrac{60}{2}$$ mL of 0.5M

H2SO4 = 30 mL of 0.5 M H2SO4

Acid consumed in absorption of evolved ammonia is (50–30) mL = 20 mL

Again, 20 mL of 0.5 MH2SO4 = 40 mL of 0.5 MNH3

Also, since 1000 mL of 1 MNH3 contains 14 g of nitrogen,

40 mL of 0.5 MNH3 will contain = $$\dfrac{14\times 40}{1000}\times 0.5$$

= 0.28 g of N

Therefore, percentage of nitrogen in 0.50 g of organic compound

$$\dfrac{0.28}{0.50}\times 100$$ = 56 %

Answered by Pragya Singh | 1 year ago

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