NEET 2022 Chemistry Kjeldahl’s Method MCQ Question

Chapter: Organic Chemistry – Some Basic Principles & Techniques

Class: 11 | Topic: Kjeldahl’s Method | Difficulty: 🟡 Medium

✅ Ans: A — Aniline $(C_6H_5NH_2)$

Kjeldahl’s method works when the nitrogen is converted into $NH_4^+$ / ammonium sulfate during digestion with concentrated $H_2SO_4$.

• A: Aniline $(C_6H_5NH_2)$ ✅ → nitrogen can be converted to ammonium sulfate → estimation possible.
• B: Azobenzene $(C_6H_5-N=N-C_6H_5)$ ❌ → azo $(-N=N-)$ nitrogen is not converted.
• C: Nitrobenzene $(C_6H_5NO_2)$ ❌ → nitro $(-NO_2)$ nitrogen is not converted.
• D: Pyridine ❌ → nitrogen is part of an aromatic ring and is not converted to ammonium sulfate. (Careers360)

📌 NCERT: Kjeldahl’s method is not applicable to compounds containing nitrogen in nitro groups, azo groups, or rings such as pyridine, because this nitrogen does not convert to ammonium sulfate under the reaction conditions. (Static PW Live)

🧠 NEET Trick: $-NH_2$ → YES ✅ $-NO_2$, $-N=N-$, ring $N$ → NO ❌

Cross-check: The green tick on B in your image is incorrect. The correct option for the displayed ordering is A (Aniline).