1. The problem statement, all variables and given/known data Caculate the pH at which Magnesium Hydroxide begins to precipitate from a solution containing 0.1M Mg2+ ion? Ksp=10^-11 2. Relevant equations 3. The attempt at a solution I did not understand why Ksp is given. Since the concentration of Mg2+ is 0.1, concentration of OH- will be 0.2 (by stoichiometry). Moreover there is no other source of OH-. Where am I wrong?