What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? Water and Life What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? A) pH 2 B) pH 4 C) pH 10 D) pH 12 E) pH 14 Answer: A Share this Share on FacebookTweet on TwitterPlus on Google+