question

Q 1.         What is the equivalent wt. of KMnO4 in :

            (a) Acidic Medium (b) Neutral Medium (c) In alkaline Medium

Ans.    (a)       In Acidic Medium the reaction is :

                        5 e– + 8 H+ + MnO4– ———® 4 H2O + Mn2+

                        M/5 =158/5 = 31.6 g

            (b)       In Neutral Medium the reaction is :

                        MnO4– + 2 H2O + 3 e– ———® MnO2 + 4 OH–

                        \ eq. wt. = M/3 =158/3 = 52.67

            (c)        In Alkaline Medium the reaction is :

                        (i)         Strongly Alkaline Medium

                                    MnO4– + e– ———® MnO42–

                                                                          magnate ion

                                   M/1 =158/1  = 158

                        (ii)        In Weakly Alkaline Medium the reaction is :

                                    MnO4– + 2 H2O + 3 e– ———® MnO2 + 4 OH–

                                    Same as in neutral medium

                                  M/3 =158/3  = 52.67

 

Q 2 . Sc3+ is more stable than Sc2+.

Ans.    Sc = 1s² 2s² 2p6 3s² 3p6 3d¹ 4s²

                     Sc3+ = 1s² 2s² 2p6 3s² 3p6

          

                 Inert gas configuration \ more stable