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.