Question

Question 12.22 Differentiate between the principle of estimation of nitrogen in an organic compound by

(i) Dumas method and

(ii) Kjeldahl’s method.

Class XI Organic Chemistry : Some Basic Principles and Techniques Page 363

Answer 1

(i) DUMAS METHOD : A known mass of organic compound is heated with excess of CuO in an atmosphere of CO2 , when nitrogen of organic compound is converted into N2 gas . The volume of N2 is obtained is converted into NTP and then percentage of Nitrogen determined by applying the equation ,

% of N = {28/22400 } × {vol of N2 at NTP/mass of substance taken} × 100

(ii) KJELDAHL'S METHOD :- a known mass of the organic compound is heated with conc. H2SO4 in the presence of K2SO4 {for rasing the b.p of H2SO4} and little CuSO4 or Hg as catalyst in a long necked flask called KJELDAHL'S flask when Nitrogen is present in the organic compound is quantitatively converted into (NH4)2SO4.(NH4)2SO4 thus obtained is boiled with excess of NaOH solution to liberate NH3 gas which is absorbed in know excess of standard acid such as HCl.

The volume of acid unused is found by titration against a standard alkali solution. from the volume of acid used , the percentage of N is determined by the applying below equation ,

% of N = {1.4 × molarity of acid × basicity of the acid × volume of the acid used }/mass of the substance taken.

Answer 2

Answer:

Explanation:

same