AQA Jan 2011 Paper 5 Q4

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do not write outside the box three characteristic properties of transition metals are complex formation coloured ions and catalytic activity a state the feature of transition metals that gives rise to these characteristic properties mark b state a fourth characteristic property of transition metals mark c for each of the following shapes of complex identify an appropriate example by drawing its structure c i a linear complex c ii a square planar complex c iii a tetrahedral complex question continues on the next page mark mark mark turn over wmp jan chem do not write outside the box d the chemical industry makes use of the catalytic activity of transition metal compounds for example vanadium v oxide is used as a heterogeneous catalyst in the contact process d i write an equation for the overall reaction in the contact process mark d ii explain the meaning of the term heterogeneous as applied to a catalyst mark d iii write two equations to illustrate how vanadium v oxide acts as a catalyst in the contact process equation equation marks d iv suggest what is done to a heterogeneous catalyst such as vanadium v oxide to maximise its efficiency and how this is achieved marks wmp jan chem do not write outside the box e the porphyrin ring is a multidentate ligand that is found in living systems complexed with iron ii ions in haemoglobin and with cobalt ii ions in vitamin b e i give the meaning of the term multidentate mark e ii a porphyrin ring can be represented by the symbol pr it reacts with aqueous iron ii ions as shown in the equation below the enthalpy change for this reaction is approximately zero pr aq fe h o aq fepr h o aq h o i explain why the free energy change for this reaction is negative marks e iii in vitamin b the cobalt ii ion is co ordinated to a porphyrin ring a cyanide cn ion and an additional unidentate ligand the cyanide ion is very toxic predict the co ordination number of the cobalt ion in vitamin b suggest why vitamin b is not toxic co ordination number reason why vitamin b is not toxic marks turn over wmp jan chem

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