A weak acid,HF,is in solution with dissolved sodium fluoride,NaF.If HCl is added,which ion will react with the extra hydrogen ions from the HCl to keep the pH from changing? A)Na⁺ B)OH^- C)Na^- D)F^- E)none of these

Question

Quizplus · Accepted Answer

When HCl is added, it will donate extra hydrogen ions (H+) to the solution. 
As HF is a weak acid, it will only partially dissociate into H+ and F-. 
Therefore, the added H+ ions will react with the F- ions from the dissolved NaF to form HF, which will help maintain the pH of the solution. 
So, the ion that will react with the extra hydrogen ions to keep the pH from changing is F- from NaF, making option D the correct answer.

A Weak Acid,HF,is in Solution with Dissolved Sodium Fluoride,NaF