1. 1 Born-Haber Cycles enthalpy H magnesium chloride MgCl 2 (s) Mg 2+ (g) + 2Cl - (g) H lattice Mg (s) + Cl 2 (g) H formation H atomisation Mg (g) + Cl 2 (g) H first ionisation energy Mg + (g) + e - + Cl 2 (g) Mg 2+ (g) + 2e - + 2Cl (g) H second ionisation energy 2 x H first electron affinity Mg 2+ (g) + 2e - + Cl 2 (g) H bond energy of chlorine Mg (s) + Cl 2 (g)

2. 2 Born-Haber Cycles enthalpy H magnesium chloride MgCl 2 (s) Mg 2+ (g) + 2Cl - (g) H lattice Mg (s) + Cl 2 (g) H formation H atomisation Mg (g) + Cl 2 (g) H first ionisation energy Mg + (g) + e - + Cl 2 (g) Mg 2+ (g) + 2e - + 2Cl (g) H second ionisation energy 2 x H first electron affinity Mg 2+ (g) + 2e - + Cl 2 (g) H bond energy of chlorine

3. 3 Apply Hess’s Law to calculate ∆H Lattice Energy for MgCl 2 setting out the values in a methodical manner: 1 = 2 + 3 + 4 + 5 + 6 + 7 -641 = +148 + 738 + 1451 + 242 + (2x-364) + ∆H LE -641 = + 1851 + ∆H LE ∆H LE = - 1851 - 641 = - 2492 kJ mol -1