Recall that lattice energy is the energy required to combine two gaseous ions into a solid ionic compound:
M+(g) + X–(g) → MX(s)
To calculate for lattice energy, we need to do the Born-Haber cycle for MX.
We start with the corresponding formation equation for MX:
M(s) + ½ X2(g) → MX(s), ΔH˚f
Consider an ionic compound, MX, composed of generic metal M and generic, gaseous halogen X.
The enthalpy of formation of MX is ΔHf° = -453 kJ/mol. The enthalpy of sublimation of M is ΔHsub = 127 kJ/mol. The ionization energy of M is IE = 431 kJ/mol. The electron affinity of X is ΔHEA = -301 kJ/mol. The bond energy of X2 is BE = 171 kJ/mol.
Determine the lattice energy of MX
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