How to Calculate Born-Haber Cycle
What is Born-Haber Cycle?
The Born-Haber cycle applies Hess's Law to ionic compound formation, using a thermodynamic cycle to calculate lattice energy indirectly from measurable quantities: enthalpy of formation, sublimation energy, ionisation energy, electron affinity, and bond dissociation energy.
Step-by-Step Guide
- 1ΔHf = ΔH_sub + IE + ½BE + EA + U (lattice energy)
- 2Rearrange to find U (lattice energy)
- 3All steps must sum to the enthalpy of formation
- 4Each step corresponds to a specific physical/chemical process
Worked Examples
Input
NaCl: ΔHf=−411, Sub=108, IE=496, ½BE=121, EA=−349 kJ/mol
Result
U(lattice) = −411−108−496−121+349 = −787 kJ/mol
Standard Born-Haber cycle for NaCl
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