The precise value of the lattice energy may not be determined experimentally, because of the impossibility of preparing an adequate amount of gaseous ions or atoms and measuring the energy released during their condensation to form the solid. However, the value of the lattice energy may either be derived theoretically from electrostatics or from a thermodynamic cycling reaction, the so-called Born–Haber cycle. The relationship between the molar lattice energy and the molar lattice enthalpy is given by the following equation: \Delta _G U=\Delta _G H -p\Delta V_m, where \Delta _G U is the molar lattice energy, \Delta _G H the molar lattice enthalpy and \Delta V_m the change of the volume per mol. Therefore the lattice enthalpy further takes into account that work has to be performed against an outer pressure p.
Posted on: Fri, 09 Jan 2015 07:01:24 +0000
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