5.1 Acid-Base Ionization Reactions
The acid-ionziation reaction is defined as an acid reacting with a solvent such as water.
\[\color{green}{\mathrm{HA}}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{H_3O^+} + \color{red}{\mathrm{A^-}}\]
and has the equilibrium expression
\[K_{\mathrm{a}}=\dfrac{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\left[\color{red}{\mathrm{A}^{-}}\right]}{[\color{green}{\mathrm{HA}}]}\]
A strong acid has a Ka that is large (generally 1 or greater) whereas a weak acid has a Ka that is less than 1.
The base-ionization reaction is defined as a base reacting with a solvent such as water.
\[\color{red}{\mathrm{B}}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{OH^–} + \color{green}{\mathrm{HB^+}}\]
and has the equilibrium expression
\[K_{\mathrm{b}}=\dfrac{\left[\mathrm{OH}^{-}\right]\left[\color{green}{\mathrm{HB}}^{+}\right]}{[\color{red}{\mathrm{B}}]}\]
Alternatively, we can express the reaction as
\[\color{red}{\mathrm{A^-}}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{OH^–} + \color{green}{\mathrm{HA}}\]
\[K_{\mathrm{b}}=\dfrac{\left[\mathrm{OH}^{-}\right]\left[\color{green}{\mathrm{HA}}\right]}{[\color{red}{\mathrm{A^-}}]}\] A strong base has a Kb that is large (generally 1 or greater) whereas a weak base has a Kb that is less than 1.