Question

The percentage of pyridine $C_5{H}_{5}N$ that forms pyridinium ion $\left(C_5{H}_5{N}^{+}H\right)$ in a 0.10 M aqueous pyridine solution $(K_b$ for $C_5{H}_{5}N=1.7\times {10}^{-9})$ is

• A. 0.77%
• B. 1.6%
• C. 0.0060%
• D. 0.013%

Answer 1

The correct option is D 0.013%

Pyridine $\left(C_5{H}_{5}N\right)$ is a weak base $K_b=C{\alpha }^2$
$\alpha =\sqrt{\frac{1.7\times {10}^{-9}}{0.1}}$
$\alpha =1.30\times {10}^{-4}$
$\%\alpha =1.30\times {10}^{-4}\times 100$
$\%\alpha =0.013\%$