choice of a suitable colour filter brief description of a colorimeter brief

Choice of a suitable colour filter brief description

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choice of a suitable colour filter brief description of a colorimeter. brief description of the colour absorption properties of complexes calibration of the colorimeter comparison with other methods 16
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Section 11/ The d-Block Elements / Suggested solutions / ‘Stoichiometry of complex by titration’ e.g. Ni 2+ -EDTA complex. prepare standard solutions of Ni 2+ and EDTA place a known volume of the Ni 2+ solution with a few drops of murexide in a conical flask. add EDTA from a burette until the murexide changes colour. stoichiometry of complex = mole ratio of Ni 2+ to EDTA Optional marks (any two) EDTA is a stronger ligand than murexide Ni-EDTA complex and Ni-murexide complex are of different colour. limitation of the method comparison with other methods. (accept other experimental methods) 95 IIB Q.6 (a) Electronic configuration of Ti atom : 3d 4s 1s 2 2s 2 2p 6 3s 2 3p 6 3d 2 4s 2 / [Ar] ↑↓ (accept any correct form of electronic configuration.) [1] (b) Ti metal : In the production of supersonic aircraft body. or, Space shuttle. [1] Ti compound : TiO 2 paint filler. [1] or, Polymerisation catalyst in Ziegler/Natta process. (TiCl 4 /AlEt 3 ) in polymerization of ethylene. (accept any correct use of Ti and Ti compounds) (c) (i) octahedral [1] (ii) The colouration in transition metal ion is due to absorption of energy in uv-visible region by d-electrons when they are excited from one energy level to the other . [1] In TiO 2+ (aq), there is no d electron (d 0 ) / no d-d transition is possible . [1] it is colourless. In [Ti(H 2 O) 6 ] 3+ ion, the presence of 3d electron (d 1 ) cause the violet colour in solution due to d-d transition . [1] (iii) From the E ° values, O 2 is a stronger oxidizing agent than TiO 2+ . At standard conditions, the E ° of the following reaction is +1.23 - (+0.11)V = +1.12V [2] (Deduct [1] for no indication of + sign.) 4Ti 3+ (aq) + O 2 (g) + 2H 2 O(l) → 4TiO 2+ (aq) + 4H + (aq) [1] In the presence of oxygen, [Ti(H 2 O) 6 ] 3+ will be oxidized to TiO 2+ (aq) / the violet solution will turn colourless. [1] 96 IA Q.2 (e) (i) [Fe(H 2 O) 6 ] 3+ [ ½ ] The conjugate base [Fe(H 2 O) 5 OH] 2+ is stabilized to a greater extent because the [ ½ ] anionic ligand OH - tends to stabilize the electron deficient Fe 3+ more than Fe 2+ / [ ½ ] causes the eqm. to lie towards the right / increase the ease of ionization of H . [ ½ ] or, Fe 3+ has a higher charge to radius ratio /charge density , greater polarizing power , ( ½ + ½ ) and hence the H develops larger partial +ve charge . ( ½ ) 17
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Section 11/ The d-Block Elements / Suggested solutions / (ii) HClO 4 [ ½ ] the conjugate base ClO 4 - possesses a larger no. of oxo group (O atoms) is [ ½ ]+[ ½ ] stabilized to a greater extent by resonance/mesomeric effect . [ ½ ] or, In HClO 4 , the Cl has a higher oxidation state and a larger number of oxo groups (O atoms ), ( ½ + ½ ) which can induce a higher positive charge density on H . ( ½ ) (ii) HMnO 4 [ ½ ] The conjugate base MnO 4 - possesses a large no. of oxo group then HCrO 4 - is [ ½ ]+[ ½ ] stabilized to a greater extent by resonance/mesomeric effect . [ ½ ] or, Mn has a higher O.S. than Cr , MnO 4 - is singly charged while CrO 4 2- is doubly (
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  • Spring '08
  • FLEET
  • Oxidation Number, D-block elements, NH3, Ion, SUGGESTED SOLUTIONS

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