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 X_{2}(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 ΔH_{f}° = -453 kJ/mol. The enthalpy of sublimation of M is ΔH_{sub} = 127 kJ/mol. The ionization energy of M is IE = 431 kJ/mol. The electron affinity of X is ΔH_{EA} = -301 kJ/mol. The bond energy of X_{2} is BE = 171 kJ/mol.

Determine the lattice energy of MX

____ kJ/mol

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