If the pKa of HCOOH is 3.74 and the pH of an HCOOH/HCOONasolution is 3.11, which of the following is TRUE? A) [HCOOH] [HCOONa]

Question

If the pKa of HCOOH is 3.74 and the pH of an HCOOH/HCOONasolution is 3.11, which of the following is TRUE? A) [HCOOH] < [HCOONa] B) [HCOOH] = [HCOONa] C) [HCOOH] << [HCOONa] D) [HCOOH] > [HCOONa] E) [HCOOH] >> [HCOONa]

Quizplus · Accepted Answer

The pH of the solution (3.11) is lower than the pKa of HCOOH (3.74), which means that the solution is more acidic than the dissociation constant of HCOOH. This indicates that the majority of HCOOH molecules have dissociated into H+ ions and HCOO- ions. Since HCOONa is a salt of HCOO-, it will dissociate completely in solution, producing Na+ ions and HCOO- ions. Therefore, the concentration of HCOO- ions in the solution will be much higher than the concentration of undissociated HCOOH molecules. As a result, [HCOOH] > [HCOONa] is the correct answer, making option D the correct choice.

If the PKa of HCOOH Is 3