OCR A Jun 2015 Paper 5 Q1

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Answer all the questions. This question looks at properties of transition elements, ions and complexes. (a) What is the oxidation number of Cr in the complex ion [CrOCl5]2?[1] (b) Write the equation for a reaction catalysed by a named transition element, compound or ion. Equation:Catalyst:[1] (c) An octahedral complex ion A, C9H30N6Ni3+, exists as two optical isomers. In complex ion A, Ni3+ is bonded to three molecules of a bidentate ligand B. (i) State what is meant by a bidentate ligand.[1] (ii) What is the molecular formula of the bidentate ligand B?[1] (iii) Draw a possible structure for B and explain how B is able to act as a bidentate ligand.[2] (iv) What is the coordination number of complex ion A?[1]OCR 2015<br />
 (v) Complete the 3-D diagrams of the shapes of the optical isomers of complex ion A. You can show the bidentate ligand simply as 3+ 3+ Ni Ni [1] (d) Describe the reactions of EITHER aqueous copper(II) ions OR aqueous cobalt(II) ions with: aqueous sodium hydroxide excess aqueous ammonia hydrochloric acid.In your answer you should link observations with equations.[6]OCR 2015 [Total: 14] Turn over<br />

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