The percentage of pyridine (C_5H_5N) that forms pyridinium ion (C_5H_5N^+H) in a 0.10 M aqueous pyridine solution (K_b for C_5H_5N = 1.7×10^-9) is

1. $0.013\%$

2. $0.77\%$

3. $1.6\%$

4. $0.0060\%$

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 2 Practice test neet Save WhatsApp Report

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Answer: 1. $0.013\%$

Key idea: for a weak base, $\alpha=\sqrt{K_b/C}$.

$$\alpha=\sqrt{\frac{1.7\times10^{-9}}{0.10}}=\sqrt{1.7\times10^{-8}}=1.3\times10^{-4}$$

Percentage = $1.3\times10^{-4}\times100=0.013\%$.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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