Chemistry - Ionic Equilibrium Question with Solution | TestHub

$\text{HA}+\text{aq}\rightleftharpoons {\underset{\text{aq}}{\text{H}}}^{+}+\underset{\text{aq}}{{\text{A}}^{-}}$

${\text{K}}_{\text{a}}=\frac{\left[{\text{H}}^{+}\right]\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$

Also$\text{HA}+{\text{B}}^{+}+{\text{OH}}^{-}\rightleftarrows {\text{B}}^{+}+{\text{H}}_2\text{O}+{\text{A}}^{-}$

$\text{HA}+{\text{OH}}^{-}\rightleftharpoons {\text{H}}_2\text{O}+{\text{A}}^{-}$

${\text{K}}_{\text{eq}}=\frac{\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]\left[{\text{OH}}^{-}\right]}=\frac{\left[{\text{A}}^{-}\right]\left[{\text{H}}^{+}\right]}{\left[\text{HA}\right]\left[{\text{OH}}^{-}\right]\left[{\text{H}}^{+}\right]}=\frac{\text{K}a}{\text{K}w}$

$\therefore$${\text{K}}_{\text{eq}}=\frac{{\text{K}}_{\text{a}}}{{\text{K}}_{\text{w}}}=\frac{{10}^{-4}}{{10}^{-14}}={10}^{10}$