Oxidation-Reduction

 

10) (b)

                                        +5 -6                    +3  +3 -6
                               0            -2                    +1        -2       +1+1-2

                     As + ClO3- H3AsO3 + HClO

 

                     oxidation:

                                   As  H3AsO3

                                   As  H3AsO3 + 3e-

                     As + 3H2O  H3AsO3 + 3e-

                     As + 3H2O  H3AsO3 + 3H+ + 3e-

 

                     reduction:

                               ClO3- HClO

                      ClO3- + 4e- HClO

                          ClO3- + 4e- HClO + 2H2O

           ClO3- + 5H+ + 4e- HClO + 2H2O

 

                                                                                   6

                                                  4As + 12H2O 4H3AsO3 + 12H+ + 12e-

                                                                         3

                                     3ClO3- + 15H+ + 12e- 3HClO + 6H2O
                       _______________________________________________________________

                        4As(s) + 3ClO3-(aq) + 3H+(aq) + 6H2O(l) 4H3AsO3(aq) + 3HClO(aq)

 

                        As is the reducing agent and ClO3- is the oxidizing agent.

 

      (f)

                            +2  -2      +14 -14                +3  -4
                            +1  -1        +7  -2                        -2         0

                     H2O2 + Cl2O7 ClO2- + O2

 

                     oxidation:

                               H2O2  O2

                               H2O2  O2 + 2e- + 2H+

                     

                     reduction:

                              Cl2O7 ClO2-

                              Cl2O7 2ClO2-

                         Cl2O7 + 8e- 2ClO2-

                     Cl2O7 + 8e- 2ClO2- + 3H2O

           Cl2O7 + 8e- + 6H+ 2ClO2- + 3H2O

 

                                                                                                                              2

                                                  4H2O2  4O2 + 8e- + 8H+

                                                                        

                                          Cl2O7 + 8e- + 6H+ 2ClO2- + 3H2O
                           _____________________________________________________________

                                     4H2O2 + Cl2O7 4O2 + 2ClO2- + 3H2O + 2H+

                                                    2OH-                                                                     2OH-
                                    
_____________________________________________________________

                           4H2O2(aq) + Cl2O7(aq) + 2OH-(aq) 4O2(g) + 2ClO2-(aq) + 5H2O(l)

 

                       H2O2 is the reducing agent and Cl2O7 is the oxidizing agent.