S2- + H2O = HS- + OH- ；HS- + H2O = H2S + OH-
Fe3+ + 3 H2O = Fe(OH)3 + 3 H+
Cu2+ + 2 H2O = Cu(OH)2 + 2 H+
PO43- + H2O = HPO42- + OH-；HPO42- + H2O = H2PO4- + OH-；
H2PO4-+ H2O = PO43- + OH-