5.0 x 10-9 M H3O+ and 2.0 x 10-6 M OH- Explanation: To find H3O+, do the following: pH = -log[H3O+] -pH = log[H3O+] antilog -(8.3) = antilog log (antilog and log cancel out) [H3O+] 5.0 x 10^-9 = [H3O+] To find OH, you need to know pOH pOH = 14 - pH pOH = 14 - 8.3 pOH = 5.7 To find OH-, use a similar formula to the one above: pOH = -log [OH-] -pOH = log [OH-] antilog - (5.7) = antilog log (antilog and log cancel out) [OH-] 2.0 x 10^-6 = [OH-]