A 0.15 M solution of chloroacetic acid has a pH of 1.86. What is the value of K_a for this acid?

Question

Quizplus · Accepted Answer

The pH of the solution is given as 1.86, which means the concentration of H+ ions is 10^-1.86. For a weak acid like chloroacetic acid, the concentration of H+ ions is approximately equal to the square root of the product of the acid dissociation constant (Ka) and the initial concentration of the acid. Using the formula [H+]^2 = Ka * [Acid], where [H+] = 10^-1.86 and [Acid] = 0.15 M, we can solve for Ka. Rearranging the formula gives Ka = [H+]^2 / [Acid]. Substituting the values gives Ka ≈ 1.4 × 10^-3, which matches choice D.

A 015 M Solution of Chloroacetic Acid Has a PH of of 1.86