If a solution of HF (Ka = 6.8x10-4) has a pH of 3.65, calculate the concentration of hydrofluoric acid.

Answer 1

HF ==> H⁺ + F^-

pH = 3.65

[H⁺] = 1x10^-3.65 = 2.24x10^-4 M

Ka = [H+][A-] / [HA]

6.8x10^-4 = (2.24x10^-4)² / [HA]

[HA] = 7.38x10^-5 M