OCR A Jun 2015 Paper 5 Q5

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Iron(II) iodide, FeI2, is formed when iron metal reacts with iodine. (a) The table below shows enthalpy changes involving iron, iodine and iron(II) iodide. 14 Formation of iron(II) iodide 1st electron affinity of iodine 1st ionisation energy of iron 2nd ionisation energy of iron Atomisation of iodine Atomisation of iron Enthalpy change / kJ mol1 113 295 +759 +1561 +107 +416 (i) The incomplete BornHaber cycle below can be used to determine the lattice enthalpy of iron(II) iodide. In the boxes, write the species present at each stage in the cycle. Include state symbols for the species. Fe2+(g) + 2I(g) + 2e Fe(s) + 2I(g)OCR 2015 FeI2(s) [4]<br />
 (ii) Define the term lattice enthalpy. 15[2] (iii) Calculate the lattice enthalpy of iron(II) iodide. lattice enthalpy =kJ mol1 [2]OCR 2015 Turn over<br />
 (b) Some electrode potentials for ions are shown below. 16 Fe2+(aq) + 2e Fe3+(aq) + e I2(aq) + e Br2(aq) + e Cl 2(aq) + e Fe(s) Fe2+(aq) I(aq) Br(aq) Cl (aq) E o = 0.44 V E o = +0.77 V E o = +0.54 V E o = +1.09 V E o = +1.36 V (i) Complete the electron configurations for Fe2+ and Br. Fe2+: 1s2Br: 1s2[2] (ii) Predict the products of reacting Fe(s) separately with I2(aq), Br2(aq) and Cl 2(aq). Explain your predictions using the electrode potential data above.[3]OCR 2015<br />
 17ions. (c) Fe2+ ions can be used to test for NO3ions, followed by In this test, aqueous iron(II) sulfate is added to a solution containing NO3 slow addition of concentrated sulfuric acid. The sulfuric acid forms a layer below the aqueous solution. In the presence of NO3ions, a brown ring forms between the two layers. Two reactions take place. Fe2+ ions are oxidised to Fe3+ ions. Water also forms. Reaction 1: In the acid conditions Fe2+ ions reduce NO3 Reaction 2: A ligand substitution reaction of [Fe(H2O)6]2+ takes place in which one NO ligand exchanges with one water ligand. A deep brown complex ion forms as the brown ring.ions to NO. Construct equations for these two reactions. Reaction 1:Reaction 2:[3] [Total: 16]OCR 2015 Turn over<br />

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