4   2 Ammonium cobalt(II) sulfate is made by mixing aqueous solutions of ammonium sulfate and excess cobalt(II) sulfate. (a) Dry crystals of ammonium cobalt(II) sulfate, (NH4)2SO4·CoSO4·6H2O, are obtained by the procedure shown. Step 1    The reaction mixture is transferred to an evaporating basin, heated gently and then left to crystallise. Step 2    The crystals are separated by gravity filtration. Step 3    The crystals are then rinsed with a small amount of ice‑cold water. Step 4    The rinsed crystals are placed in a warm oven for 30 minutes. (i) The colour of the cobalt(II) sulfate solution used is pink due to the complex cobalt(II) ion, [Co(H2O)6]2+. Explain why the solution is coloured. 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(ii) Explain the shape of the cobalt(II) ion, [Co(H2O)6]2+ , using electron‑pair repulsion theory. 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Turn over 5   (iii) Give the reasons for carrying out Steps 3 and 4 of the procedure, referring particularly to the words in bold. 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(b) The percentage yield of this reaction is 70.0 %. Give two possible reasons, other than an incomplete reaction, why the yield is less than 100 %. 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(Total for Question 2 = 12 marks)