3 BaCl₂  +  Fe₂ (SO₄)₃                3 BaSO₄  +  2 FeCl₃__________________________________

S    +    Mg                  MgS                            __________________________________

4 Na    +    O₂                        2Na₂O                __________________________________

CuO    +     H2O                     Cu (OH)₂ +         __________________________________

Mg    +    H₂SO₄                      MgSO₄    +    H₂   __________________________________

2 Fe    +    3 H2O                     Fe2O3   +   3 H₂ __________________________________

2 Al    +    Fe₂O₃                    Al₂O₃    +    2 Fe