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

       Kw = [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