CIE Jun 2017 v2 Paper 4 Q4

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PMT 10 (a) A number of isomers with the formula Cr(H2O)6Cl 3 exist. Their general formula is [Cr(H2O)6-nCl n]Cl 3-n.nH2O. Each isomer contains a six co-ordinated Cr(III) ion in an octahedral complex. Water molecules not directly bonded with the Cr atom are held in the crystal lattice as water of crystallisation. The CrCl bond is not easily broken and so chloride bonded with the Cr(III) ion in the complex does not react. 1.00 g samples of three of the isomers, A, B and C, were dissolved in separate samples of water. An excess of AgNO3(aq) was added to each and the mass of AgCl (s) formed was measured. Ag+(aq) + Cl (aq) AgCl (s) The number of moles of AgCl (s) formed was calculated. The table shows the results. isomer moles of AgCl formed from 1.00 g of isomer A B C 3.75103 7.50103 1.13102 (i) Calculate the Mr of Cr(H2O)6Cl 3. Mr Cr(H2O)6Cl 3 =[1] (ii) Use the data in the table above to calculate the value of n for each of the isomers, A, B and C. Complete the table below with the values of n and the molecular formula of each isomer, in the style of the general formula given above. Show your working for at least one calculation of n. isomer molecular formula [2]UCLES 2017 9701/42/M/J/17<br /> PMT 11 (b) Two isomers have the same shape and their formula is Ni(R3P)2(CN)2, where R = CH3. Only one of these isomers has a dipole moment. (i) Name the type of isomerism shown by Ni(R3P)2(CN)2.[1] (ii) Draw structures of these two isomers. isomer 1 isomer 2 [1] (iii) State which isomer has a dipole moment. Explain your answer.[1] [Total: 6]UCLES 2017 9701/42/M/J/17 [Turn over<br />

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