Chemistry - Ionic Equilibrium Question with Solution | TestHub

$$\text{ The hydrolysis reaction of conjugate base of acid is }$$ $$\begin{array}{c}{A}^{-}(aq)+{\mathrm{H}}_2\mathrm{O}⟶{\mathrm{HO}}^{-}+\mathrm{HA}\\ K_h=\frac{K_w}{K_a}=\frac{10^{-14}}{10^{-4}}=10^{-10}\end{array}$$ Since, degree of hydrolysis is negligible; $$\left[{\mathrm{OH}}^{-}\right]=\sqrt{K_{h}C}=10^{-6}\cdot p[\mathrm{OH}]=6\text{ and }\mathrm{pH}=14-6=8$$