Since the reaction is carried out with reactants in elemental forms and products in their standard states, at 1 bar, the overall enthalpy change of the reaction is also the enthalpy of formation for NaCl. Let us use the Born - Haber cycle for determining the lattice enthalpy of NaCl as follows:

∆H f - enthalpy change for the formation of solid MX directly form elements According to Hess's law of heat summation U - the lattice enthalpy for the formation of solid MX ∆H 3- Ionisation energy for M(g) to M +(g) ∆H 4 - electron affinity for the conversion of X(g) to X -(g) ΔH 2- enthalpy change for the dissociation of ½ X 2 (g) to X(g) ∆H 1 - enthalpy change for the sublimation M(s) to M(g) For example consider the formation of a simple ionic solid such as an alkali metal halide MX, the following steps are considered. The Born–Haber cycle applies Hess's law to calculate the lattice enthalpy.

The cycle is concerned with the formation of an ionic compound from the reaction of a metal with a halogen or other non-metallic element such as oxygen.īorn–Haber cycle is primarily used in calculating lattice energy, which cannot be measured directly. It was named after two German scientists Max Born and Fritz Haber who developed this cycle. The Born–Haber cycle is an approach to analyse reaction energies.

Born haber cycle problems pdf