question_answer

  (a) An orange solid (A) on heating gives a colourless gas (5). The gas (B) in dry condition is passed over heated Ca to give a solid (C). The solid (C) further reacts with water to produce gas (C) which forms a blue coloured compound (£) on reaction with copper sulphate solution. Identify A, B, C, D, E and give the sequence of reactions involved.                                                                                                                                                       [3] (b) Arrange the following in the order of property indicated for each set. (i) HCl, HBr, HI, HF. Decreasing thermal stability. (ii) Xe, He, Kr, Rn, Ne. Decreasing order of electron gain enthalpy.                                                                            [2] Or (a) Give reason (i) Solid  is an ionic compound.                         (ii) Ozone is thermodynamically unstable. (iii) Most of the reactions of fluorine are exothermic. (b) Draw the structures of the following. (i)                                             (ii)                                                                                                                       [3+2]

Answer:

  (a) (A)   (b) (c)                         (d) (e)                                     [1] Reactions Orange in colour (Calcium nitride) [1] (b)(i) (ii) Or (a) (i) Solid ionises as Tetrahedral Octahedral                                  [1] (ii) is thermodynamic unstable since its decomposition into is an exothermic change.                        Since, randomness increases due to increase in number of molecules hence entropy also increases. We know                      Thus,                             Thus, conversion of  into  is spontaneous taking place with decrease in free energy. Hence,  is thermodynamic unstable.                                                           [1] (iii) Most of the reactions of F^ are exothermic due to the small and strong bond formation with other elements.                   [1] (b) (i) Structure of Square pyramidal, (ii) Structure of Each P-atom is sp3 hybridised.