CIE Jun 2017 v3 Paper 4 Q3

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Bubbling air through different aqueous mixtures of CoCl 2, NH4Cl and NH3 produces various complex ions with the general formula [Co(NH3)6nCl n]3n. PMT (a) (i) Determine the oxidation state of the cobalt in these complex ions.[1] (ii) Name the two types of reaction undergone by the cobalt ions during the formation of these complex ions.[2] (iii) The complex [Co(NH3)4Cl 2]+ shows isomerism. Draw three-dimensional structures of the two isomers, and suggest the type of isomerism shown here. isomer 1 isomer 2 type of isomerism[3] (b) (i) What is meant by the term co-ordination number?[1]UCLES 2017 9701/43/M/J/17<br /> PMT (ii) Complete the table by predicting appropriate co-ordination numbers, formulae and charges for the complexes C, D, E and F. complex metal ion ligand co-ordination number formula of complex charge on complex Cr3+ Ni2+ Pt2+ Fe3+ CN H2NCH2CH2NH2 ClO2CCO2 [Fe(O2CCO2)3] 32 [6] (c) Iron(III) forms complexes in separate reactions with both SCN ions and Clions. Fe3+(aq) + SCN(aq) [FeSCN]2+(aq) Fe3+(aq) + 4Cl (aq) [FeCl 4](aq) equilibrium 1 equilibrium 2 (i) Write the expressions for the stability constants, Kstab, for these two equilibria. Include units in your answers. Kstab1 = Kstab2 = units =units =[3] (ii) An equilibrium can be set up between these two complexes as shown in equilibrium 3. [FeCl 4](aq) + SCN(aq) [FeSCN]2+(aq) + 4Cl (aq) equilibrium 3 Write an expression for Keq3 in terms of Kstab1 and Kstab2. Keq3 =[1] (iii) The numerical values for these stability constants are shown. Kstab1 = 1.4102 Kstab2 = 8.0102 Calculate the value of Keq3 stating its units. Keq3 =units =[2]UCLES 2017 9701/43/M/J/17 [Total: 19] [Turn over<br />

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