Acid-Base Equilibria

38)  pH = 12.00            [Ca(OH)₂] = ?

       Ca(OH)₂(s) Ca²⁺(aq) + 2OH^-(aq)

      
       [H⁺] = 10^-pH = 10^-12.00 = 1.0 x 10^-12 M

       K_w = [H⁺] x [OH^-] = 1.00 x 10^-14

       [OH^-] = 1.00 x 10^-14/1.0 x 10^-12 = 1.0 x 10^-2 M

       [Ca(OH)₂] = 1.0 x 10^-2 mol OH^-/L x 1 mol Ca(OH)₂/2 mol OH^- = 5.0 x 10^-3 M