(1)Cu2+ + 2OH- == Cu(OH)2
(2)Cu2+ + 2NH3.H2O == Cu(OH)2 + 2NH4+
(3)Cu2+ + S2- == CuS
(4)Cu2+ + H2S == CuS + 2H+
(5)Cu2+ + Fe == Fe2+ + Cu
(6)2Cu2+ + 3I- == 2CuI + I3-