Question

Calculate the lattice energy of LiF using the Born-Haber cycle, given the following enthalpies of formation and sublimation energies: ΔH°sub (Li) = 161 kJ/mol ΔH°sub (F2) = 155 kJ/mol ΔH°f (LiF) = - 590 kJ/mol IE (Li) = 520 kJ/mol EA (F) = -328 kJ/mol.

Answer 1

To calculate the lattice energy of LiF using the Born-Haber cycle, we need to consider the following steps:1. Sublimation of Li: Hsub  Li  = 161 kJ/mol2. Bond dissociation of F2: 1/2 Hsub  F2  = 1/2 * 155 kJ/mol = 77.5 kJ/mol3. Ionization of Li: IE  Li  = 520 kJ/mol4. Electron affinity of F: EA  F  = -328 kJ/mol5. Formation of LiF: Hf  LiF  = -590 kJ/molNow, we can use the Born-Haber cycle equation:Lattice energy = Hf  LiF  - Hsub  Li  - 1/2 Hsub  F2  - IE  Li  - EA  F Lattice energy =  -590 kJ/mol  -  161 kJ/mol  -  77.5 kJ/mol  -  520 kJ/mol  -  -328 kJ/mol Lattice energy = -590 + 161 + 77.5 + 520 + 328Lattice energy = 496.5 kJ/molSo, the lattice energy of LiF is 496.5 kJ/mol.