A solution is prepared by dissolving 0.23 mol of formic acid and 0.27 mol of sodium formate in water sufficient to yield 1.00 L of solution.The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly.The pH does not decrease drastically because the HCl reacts with the ________ present in the buffer solution.The $K _ { a }$ of formic acid is 1.36 × 10^-3. A) H₂O B) $ \mathrm{H}_{3} \mathrm{O}^{+} $ C)formate ion D)formic acid E)This is a buffer solution: the pH does not change at all upon addition of acid or base.

Question

Quizplus · Accepted Answer

The purpose of a buffer solution is to resist pH changes when an acid or base is added. In this case, the buffer solution contains both formic acid and sodium formate, which can react to maintain the pH. When HCl is added, it reacts with the formate ion (HCOO-) present in the buffer solution to form more formic acid (HCOOH) and water (H2O). This maintains the ratio of formic acid to formate ion, which in turn maintains the pH. Therefore, the correct answer is C, formate ion.

A Solution Is Prepared by Dissolving 0 KaK _ { a }Ka​

A Solution Is Prepared by Dissolving 0 $K _ { a }$