Calculation of pH
Use the same procedure as for gaseous equilibria described in Chapter 15.
Example: What is the pH of a 0.100 M HF solution? Ka = 7.0 x 10-4
HF(aq) + H2O(l) ? H3O+(aq) + F-(aq)
Ka = [H3O+][F-]/[HF] = 7.0 x 10-4
Substance HF H3O+ F-
Initial 0.100 0 0
Change -x +x +x
Equilibrium 0.100 - x x x