OCR A Jun 2013 Paper 5 Q1

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Answer all the questions. 1 BornHaber cycles can be used to determine lattice enthalpies of ionic compounds. (a) Define, in words, the term lattice enthalpy.[2] (b) The BornHaber cycle below can be used to determine the lattice enthalpy of calcium oxide. The cycle includes the values for the enthalpy changes of the steps labelled AG. (i) Complete the BornHaber cycle by adding the species present on the two dotted lines. Include state symbols.step G +798 kJ mol1 step E +1145 kJ mol1 step F 141 kJ mol1 Ca2+(g) + O(g) + e Ca+(g) + O(g) + e step D +590 kJ mol1 Ca(g) + O(g) step C +249 kJ mol1 Ca(g) + 1/2O2(g) step B +178 kJ mol1 Ca(s) + 1/2O2(g) step A 635 kJ mol1OCR 2013 lattice enthalpy CaO(s) [2]<br />
 (ii) Name the enthalpy changes for the following steps in the BornHaber cycle. step Astep Cstep G[3] (iii) Calculate the lattice enthalpy of calcium oxide. (c) Describe and explain the factors that affect the values of lattice enthalpies. answer =kJ mol1 [2][3] [Total: 12]OCR 2013 Turn over<br />

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