Born-Haber cycles are simply a fancy Hess cycle transposed onto an energy level diagram and we can use them to calculate the lattice energy for an ionic compound.
They might seem a little complicated when you first meet them but if you employ your logic skills, you will have them mastered in no time at all.
Practice question
Draw a Born-Haber cycle for potassium bromide and use it to calculate the lattice energy, ΔLEH⦵, for the process KBr(s) ⇾ K+(g) + Br–(g) .
| ΔatH⦵ /kJ mol-1 | ΔIEH⦵ /kJ mol-1 | ΔEAH⦵ /kJ mol-1 | ΔfH⦵ /kJ mol-1 | |
| Potassium | +89 | +420 | – | – |
| Bromine | +112 | – | -342 | – |
| Potassium bromide | – | – | – | -392 |
Answer
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