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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 H2SO4. - Chemistry

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Question

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 H2SO4. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

Numerical

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

= `60/2` ml of 0.5 M H2SO

= 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 M NH3 will contain

= `(14xx40)/1000xx 0.5`

= 0.28 g of N

Therefore, percentage of nitrogen in 0.50 g of organic compound

= `0.28/0.50 xx 100`

= 56 %

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Quantitative Analysis of Nitrogen
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Chapter 12: Organic Chemistry - Some Basic Principles and Techniques - EXERCISES [Page 372]

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NCERT Chemistry - Part 1 and 2 [English] Class 11
Chapter 12 Organic Chemistry - Some Basic Principles and Techniques
EXERCISES | Q 12.33 | Page 372

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