What is the percent dissociation of a benzoic acid solution with pH = 2.59? The acid dissociation constant for this monoprotic acid is 6.5 × 10^-5.

Question

Quizplus · Accepted Answer

First, we need to calculate the concentration of H+ ions in the solution using the pH:

pH = -log[H+]
2.59 = -log[H+]
[H+] = 2.12 x 10^-3 M

Now, we can use the expression for the acid dissociation constant (Ka) to calculate the percent dissociation (α) of the acid:

Ka = [H+][A-]/[HA] = 6.5 x 10^-5
(assuming that the initial concentration of benzoic acid, [HA], is equal to the concentration of undissociated benzoic acid at equilibrium)

α = [H+]/Ka x 100%
α = (2.12 x 10^-3 M)/(6.5 x 10^-5) x 100%
α = 3.26%

Therefore, the percent dissociation of the benzoic acid solution is approximately 3.5%, which corresponds to answer choice (C).

What Is the Percent Dissociation of a Benzoic Acid Solution