Chemistry - Ionic Equilibrium Question with Solution | TestHub

Explain the question:

Identify the solution with the highest pH (least acidic or most basic) among the given options. Concept:

Acidity/basicity of strong acids, weak acids, and salt hydrolysis.

Solution:

The pH of a solution decreases with increasing acidity.

1. 0.2 M HNO₃ and 0.2 M HCl: Both are strong monoprotic acids that dissociate completely in water, resulting in high $[H^{+}]$ and very low pH values ($\approx 0.7$).

2. 0.2 M CH₃COOH: This is a weak acid that only partially dissociates. Its $[H^{+}]$ is lower than that of strong acids, so its pH is higher (around 23) but still less than 7.

3. 0.2 M CH₃COONa: This is a salt derived from a weak acid (CH₃COOH) and a strong base (NaOH). In aqueous solution, the acetate ion undergoes anionic hydrolysis ($C{H}_{3}CO{O}^{-}+H_{2}O\rightleftharpoons C{H}_{3}COOH+O{H}^{-}$), releasing hydroxide ions. This makes the solution basic, with a pH greater than 7. Since this is the only basic solution, it has the maximum pH value.

Final Answer: Option (D)