CIE Nov 2017 v3 Paper 4 Q7

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(a) Complete the following electronic structures. 16 the iron atom, Fe 1s22s22p6the iron(III) ion, Fe3+ 1s22s22p6PMT [1] (b) Solutions of iron(III) salts are acidic due to the equilibrium shown. [Fe(H2O)6]3+(aq) [Fe(H2O)5(OH)]2+(aq) + H+(aq) Ka = 8.9104 mol dm3 Calculate the pH of a 0.25 mol dm3 FeCl 3 solution. (c) The table shows numerical values of the stability constants for the following equilibrium where M can be one of the metal ions listed and L one of the ligands which replaces one H2O molecule. pH =[2] [M(H2O)6]n+(aq) + L(aq) [M(H2O)5L](n1)+(aq) + H2O(l) metal ion, M ligand, L stability constant, Kstab Fe3+ Fe3+ Fe3+ Hg2+ F ClSCN Cl1.0106 2.5101 9.0102 5.0106 (i) What is meant by the term stability constant, Kstab?[1] (ii) Use the data in the table to predict the formula of the complex formed in the greatest amount when a solution containing equal concentrations of both F and SCN ions is added to Fe3+(aq),a solution containing equal concentrations of both Fe3+ and Hg2+ ions is added to Cl (aq).[1]UCLES 2017 9701/43/O/N/17<br /> PMT 17 Ethanedioate ions, O2CCO2 ethanedioate ions. , are bidentate ligands. The abbreviation ed 2 can be used to represent (d) The complex [Fe(ed )2Cl 2]3 can be formed according to the equation shown. [Fe(H2O)4Cl 2]+(aq) + 2ed 2(aq) [Fe(ed )2Cl 2]3(aq) + 4H2O(l) Write the expression for the equilibrium constant, Kstab, and state its units. Kstab = (e) [Fe(ed )2Cl 2]3 shows geometrical and optical isomerism. (i) Complete the three-dimensional diagrams to show the three stereoisomers of [Fe(ed )2Cl 2]3. You may use O O to represent ed 2. units[2] Fe Fe isomer A isomer B Fe isomer C [3] (ii) Give the letters of two isomers of [Fe(ed )2Cl 2]3 which are geometrical isomers of each other.[1] (iii) Give the letters of the two isomers of [Fe(ed )2Cl 2]3 which show optical isomerism.[1] (iv) Give the letter of the isomer which has no dipole moment.[1]UCLES 2017 9701/43/O/N/17 [Total: 13] [Turn over<br />

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