Thermo Chem Essay

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Born- Haber cycle 1. The lattice enthalpy of magnesium chloride, MgCl2, can be determined using a Born-Haber cycle and the following enthalpy changes. |Name of process |Enthalpy change/kJ mol-1 | |Enthalpy change of formation of MgCl2 |-641 | |Enthalpy change of atomization of magnesium |+148 | |First ionization energy of magnesium |+738 | |Second ionization energy of magnesium |+1451 | |Enthalpy change of atomization of chlorine |+123 | |Electron affinity of chlorine |-349 | a) Define, using an equation with MgCl2 as an example, what is meant by the term lattice enthalpy. b) Construct a Born-Haber cycle for MgCl2, including state symbols, and calculate the lattice enthalpy of MgCl2. c) Explain why the lattice enthalpy of NaBr is much less exothermic than that of MgCl2. [12] [OCR07] 1. 2. The table below shows the enthalpy changes needed to calculate the lattice enthalpy of calcium chloride,CaCl2. |Process |Enthalpy change/kJ mol-1 | |First ionization energy of calcium |+590 | |Second ionization energy of calcium |+1150 | |Electron affinity of chlorine |-348

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