Consider an aqueous buffer solution prepared by mixing equal volumes of weak acetic acid and sodium acetate of identical molar concentrations. What happens to the pH of this buffer solution when a small quantity of strong hydrochloric acid is added?

💡 Solution & Explanation

A buffer solution resists drastic changes in pH upon addition of small amounts of strong acids or bases. When hydrochloric acid is added to an acetic acid and sodium acetate buffer, the added hydrogen ions react with the acetate conjugate base present in large amounts to form weakly dissociated acetic acid, preventing significant drop in pH. Plausible distractors assume complete failure of buffering action or incorrect neutralization directions. Buffer capacity depends directly on the absolute concentrations of the weak acid and its salt.