question_answer

  (a) Assign reason for the following : (i) Transition metal ions are usually colored.                                                                                                        1 (ii) Transition elements exhibit variable oxidation state.                                                                                                 1 (iii) Interstitial compounds are well known for transition metal.                                                                                  1 (b) Give balanced chemical equation of two reactions in which acts as an oxidizing agent in acidic medium.                                                                                                                                                                                          2

Answer:

  (a) (i)  The d-orbital in transition elements are not of equal energy and d-orbital are partially filled.                                                                           As a result electron may be promoted from one d level to another d level by absorbing visible light. As a result, the compound has the colour complement to the adsorbed light. e.g., appears blue by absorbing red light.                                                                                                  (ii) Transition elements exhibit variable valency because the energy of (n - 1) d-orbital and ns orbital are of comparable energy, e.g., Sc shows + 2 and + 3 oxidation state.                                                                                   1 (iii) Because of small size of their atoms, 0 and F can form strong bonds which may also facilitate the multiple bonding.                                                                                                                                                                                               1 (b) In acidic medium, oxidizes oxalic acid into                                                                  1 or     In acidic medium, KMn04 oxidizes  into. or                                                                                                      1