The first step in the preparation of magnesium metal is the precipitation of Mg(OH)2 from sea water by the addition of Ca(OH)2. The concentration oh Mg^2+(aq) in sea water is 5.37*10^-2 M. Calculate the pH at which [Mg^2+] is diminished to 1.0*10^-5 M by the addition of Ca(OH)2.