CIE Mar 2017 v2 Paper 4 Q2

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(a) Complete the table using ticks () to indicate whether the sign of each type of energy change, under standard conditions, is always positive, always negative or could be either positive or negative. PMT always positive always negative either positive or negative energy change electron affinity enthalpy change of atomisation ionisation energy lattice energy [2] (b) The Born-Haber cycle for magnesium chloride is shown. Mg2+(g) + 2Cl (g) + 2e H4 H5 Mg2+(g) + 2Cl (g) Mg+(g) + 2Cl (g) + e H3 H2 H1 Mg(g) + 2Cl (g) Mg(g) + Cl 2(g) Mg(s) + Cl 2(g) H7 MgCl 2(s) H6 (i) Explain why H4 is greater than H3.[1] (ii) What names are given to the enthalpy changes H6 and H7? H6H7[1]UCLES 2017 9701/42/F/M/17<br /> PMT (c) Chlorine is in Group 17. Suggest the trend in the first electron affinity of the elements in Group 17. Explain your answer.[2] (d) The equation for the formation of magnesium oxide from its elements is shown. Mg(s) + 1 2O2(g) MgO(s) H o =602 kJ mol1 substance S o / J K1 mol1 Mg(s) O2(g) MgO(s) 32.7 205 26.9 Use the equation and the data given in the table to calculate G o for the reaction at 25 C. G o =units[4] [Total: 10]UCLES 2017 9701/42/F/M/17 [Turn over<br />

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