Acetic Acid will initially be 0 . 3 M , but some of it dissociates. You cannot use the H - H equation because there is not a substantial amount of acetate ion present. Use an ICE table to determine the equilibrium concentrations in terms of x , the amount of acid that dissociates. Plug into the Ka expression. Use the weak acid approximation: x is small, so a number - x can be approximated by just the number. Solve for [ H 3 O ] concentration, then convert to pH . Find: [ H 3 O ] Predicted pH of solution 8 ( 3 sig figs ) Data: Ka value of acetic acid: 1 . 7 6 e - 5 Volume of 0 . 3 M Acetic Acid used: 3 9 . 0 mL Volume of 0 . 2 M Sodium Acetate used: 6 1 . 0 mL Soln 8 ( 0 . 3 M acetic acid ) pH: 2 . 6 0