Amines
The value of pKa of anilinium ion (C6H5NH3+) at 25 C is closest to (Given: Kb of aniline = 4.3 x 10-10):
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About This Question
- Subject
- chemistry
- Chapter
- organic compounds containing nitrogen
- Topic
- amines
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
4.63
For a conjugate acid-base pair at 25 C, pKa + pKb = 14. First find pKb of aniline: pKb = -log(4.3 x 10-10) approximately 9.37. Therefore pKa of anilinium ion = 14 - 9.37 = 4.63. This low pKa is consistent with weak basicity of aniline, which arises from resonance delocalization of the lone pair on nitrogen into the benzene ring.
This hard difficulty chemistry question is from the chapter organic compounds containing nitrogen, covering the topic of amines. It appeared in the 2025 exam.
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