Kjeldahl's Method
Kjeldahl's method cannot be used for nitrogen estimation in:
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About This Question
- Subject
- chemistry
- Chapter
- purification and characterisation of organic compounds
- Topic
- kjeldahl's method
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Nitro compounds
Kjeldahl's Method is widely used but has significant limitations.
- Inability: It cannot be used for organic compounds where nitrogen is part of a Nitro group (−NO2), Azo group (−N=N−), or present in a ring (like Pyridine).
- Reason: In these compounds, nitrogen does not quantitatively convert into ammonium sulfate when heated with concentrated sulfuric acid. Instead, most of the nitrogen escapes as N2 gas during the digestion process, leading to inaccurate (too low) results.
This medium difficulty chemistry question is from the chapter purification and characterisation of organic compounds, covering the topic of kjeldahl's method. It appeared in the 2025 exam.
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