Example 13.12b: Equilibrium Concentrations in a Solution of a Weak Acid

Only a small fraction of a weak acid ionizes in aqueous solution. What is the percent ionization of acetic acid in a 0.100-M solution of acetic acid, \(\ce{CH3CO2H}\)?

\(\ce{CH3CO2H(aq)}\)\(\ce{ + }\)\(\ce{H2O(l)}\)\(\ce{<=>}\)\(\ce{H3O+(aq)}\)\(\ce{ + }\)\(\ce{CH3CO2-(aq)}\)\(\ce{ }\) \(K_{\mathrm{a}}\)\( = \)\(1.8\times 10^{-5}\)

(Hint: Determine [CH3CO2-] at equilibrium.) Recall that the percent ionization is the fraction of acetic acid that is ionized × 100％, or [CH3CO2-]/[CH3CO2H]initial×100.

Think about it...