A 0.10 M solution of a weak monoprotic acid has a pH of 3.40 at 25°C.What is the acid-ionization constant,K_a,for this acid?

Question

Quizplus · Accepted Answer

The pH of the solution is 3.40, which means the concentration of H+ ions is 10^-3.40. For a weak monoprotic acid, the acid-ionization constant (Ka) can be calculated using the formula Ka = [H+][A-]/[HA], where [HA] is the initial concentration of the acid and [H+] = [A-] for a monoprotic acid. Given [H+] = 10^-3.40 and the initial concentration [HA] = 0.10 M, we can calculate Ka = (10^-3.40)^2 / 0.10 = 10^-6.80 / 0.10 = 1.6 × 10^-6, which matches choice A.

A 010 M Solution of a Weak Monoprotic Acid Has a a PH