Chemistry - Ionic Equilibrium Question with Solution | TestHub

${\mathrm{K}}_{\mathrm{a}}$ of Butyric acid $\Rightarrow 2\times {10}^{-5} {\mathrm{pK}}_{\mathrm{a}}=-{\mathrm{logK}}_{\mathrm{a}} = 4.7$

$\mathrm{pH}$ of weak acid solution

$\mathrm{pH}=\frac{1}{2}{\mathrm{pK}}_{\mathrm{a}}-\frac{1}{2}\mathrm{logC}$

$=\frac{1}{2}\left(4·7\right)-\frac{1}{2}\log \left(0.2\right)$

$=2.35+0.35=2.7$

$\mathrm{pH}=27\times {10}^{-1}$