Chemical And Ionic Equilibrium Result Question 30
30. A certain buffer solution contains equal concentration of $\mathrm{X}^{-}$ and $\mathrm{H} X$. The $K_b$ for $X^{-}$ is $10^{-10}$. The pH of the buffer is
(1984, 1M)
(a) $4$
(b) $7$
(c) $10$
(d) $14$
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Answer:
Correct Answer: 30. ( a )
Solution:
$\begin{aligned} K_a(\mathrm{H} X) & =\frac{K_w}{K_b}=10^{-4} \\ \mathrm{pH} & =\mathrm{p} K_a+\log \frac{\left[X^{-}\right]}{[\mathrm{H} X]}\end{aligned}$
$\Rightarrow \quad \mathrm{p} K_a=4 \qquad \left[\because\left[X^{-}\right]=[\mathrm{H} X]\right]$
BETA
