Question

The following equilibrium is established when hydrogen chloride is dissolved in acetic acid $HCl+C{H}_{3}COOH\to C{l}^{-}+C{H}_{3}COO{H}_2^{+}$. The set that characterizes the conjugate acid - base pairs is:

• A. $(HCl,C{H}_{3}COOH)and(C{H}_{3}COO{H}_2^{+},C{l}^{-})$
• B. $(HCl,C{H}_{3}COO{H}_2)and(C{H}_{3}COOH,C{l}^{-})$
• C. $(C{H}_{3}COO{H}_2^{+},HCl)and(C{l}^{-},C{H}_{3}COOH)$
• D. $(HCl,C{l}^{-})and(C{H}_{3}COO{H}_2^{+},C{H}_{3}COOH)$

Answer 1

The correct option is D $(HCl,C{l}^{-})and(C{H}_{3}COO{H}_2^{+},C{H}_{3}COOH)$

Conjugate acid base pair differ by a single proton and base is one which accept proton, acid is which donates proton.

Thus HCl and $C{H}_{3}COO{H}_2^{+}$ are acids as they donate proton and $C{l}^{-}$ and $C{H}_{3}COOH$ are bases as they accept proton.