The enthalpy of formation of MX is ΔHf° = –493 kJ/mol. The enthalpy of sublimation of M is ΔHsub = 143 kJ/mol. The ionization energy of M is IE = 437 kJ/mol. The electron affinity of X is ΔHEA = –317 kJ/mol. (Refer to the hint). The bond energy of X2 is BE = 193 kJ/mol.

Question

Determine the lattice energy of MX??

Answer 1

Hformation = sub + IE + EA + 1/2*BE + Ecryst
Solve for Ecrystal, then lattice energy is - of Ecrystal.