A solution is prepared by dissolving 0.23 mol of hydrofluoric acid and 0.27 mol of sodium fluoride 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 hydrofluoric acid is 1.36 × 10^-3. A)H₂O B)H₃O⁺ C)fluoride ion D)hydrofluoric acid E)This is a buffer solution: the pH does not change upon addition of acid or base.

Question

Quizplus · Accepted Answer

A buffer solution contains a weak acid and its conjugate base, or a weak base and its conjugate acid, which can resist changes in pH. In this case, the solution contains hydrofluoric acid (the weak acid) and sodium fluoride (the conjugate base). When HCl is added, it reacts with the fluoride ion (the conjugate base) present in the buffer solution to form HF (the weak acid). This reaction helps to maintain the pH of the solution relatively stable. Therefore, the best choice is C, fluoride ion.

A Solution Is Prepared by Dissolving 0