Question

A 1.25-molar solution of a weak monoprotic acid is 9.2% ionized. Calculate the pH of the solution.

Answer 1

concentration of weak acid = 1.25 M

% ionization = 9.2 %

HA -------------> H+ + A-

1.25                    0         0

1.25 - x               x          x

% ionization = [H+] / initial ) x 100

9.2 = ([H+] / 1.25 ) x 100

[H+] = 0.115 M

pH = -log [H+] = -log (0.115)

pH = 0.94