HA <=> H+ + A- pH = -log[H+] = 4.0 [H+] = 10-pH = 10-4 M Percent ionization = [H+]/[HA] x 100% = 10-4/0.6 x 100 = 0.017% Solution HA <=> H+ + A- pH = -log[H+] = 4.0 [H+] = 10-pH = 10-4 M Percent ionization = [H+]/[HA] x 100% = 10-4/0.6 x 100 = 0.017%.