NEET 2022 · ChemistryPrevious Year Question

The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds?

Answer: (C) Aniline ( $C X_{6} H X_{5} - NH X_{2}$ ). \textbf{Answer:} (c) Aniline \textbf{Solution:} Kjeldahl's method works only when the nitrogen is quantitatively converted to ammonium sulphate $(NH X_{4}) X_{2} SO X_{4}$ on digestion with conc.

NEET 2022 Chemistry question — The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount…

A.Nitrobenzene ( $C X_{6} H X_{5} - NO X_{2}$ )
B.Pyridine (nitrogen in the aromatic ring)
C.Aniline ( $C X_{6} H X_{5} - NH X_{2}$ )✓
D.Azobenzene ( $C X_{6} H X_{5} - N = N - C X_{6} H X_{5}$ )

Correct Answer

Solution & Explanation

\textbf{Answer:} (c) Aniline \textbf{Solution:} Kjeldahl's method works only when the nitrogen is quantitatively converted to ammonium sulphate $(NH X_{4}) X_{2} SO X_{4}$ on digestion with conc. $H X_{2} SO X_{4}$ . It fails for nitrogen present as $- NO X_{2}$ (nitrobenzene), in azo groups $- N = N -$ (azobenzene), or in a ring (pyridine), because such nitrogen is not converted to ammonium sulphate. Aniline $(- NH X_{2})$ is converted to ammonium sulphate, so only aniline can be estimated by this method.

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