Chemical and Ionic Equilibrium 2 Question 30
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30. A certain buffer solution contains equal concentration of $X^{-}$ and $\mathrm{H} X$. The $K_{b}$ for $X^{-}$is $10^{-10}$. The $\mathrm{pH}$ of the buffer is
======= ####30. A certain buffer solution contains equal concentration of $X^{-}$ and $\mathrm{H} X$. The $K_{b}$ for $X^{-}$is $10^{-10}$. The $\mathrm{pH}$ of the buffer is
3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed (a) 4
(b) 7
(c) 10
(d) 14
$(1984,1 \mathrm{M})$
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Solution:
- $K_{a}(\mathrm{H} X)=\frac{K_{w}}{K_{b}}=10^{-4}$
$$ \mathrm{pH}=\mathrm{p} K_{a}+\log \frac{\left[X^{-}\right]}{[\mathrm{H} X]} $$
$$ \Rightarrow \quad \mathrm{p} K_{a}=4 \quad\left[\because\left[X^{-}\right]=[\mathrm{H} X]\right] $$
