Calculate the lattice energy for LiF(s) given the following:

Question

Quizplus · Accepted Answer

To calculate the lattice energy for LiF(s), we need to use the Born-Haber cycle.

Li(s) → Li(g) ΔHsubl = +161 kJ/mol (enthalpy of sublimation of Li)

Li(g) → Li+(g) + e- ΔHIE1 = +520 kJ/mol (first ionization energy of Li)

F2(g) → 2F(g) ΔHbond = +159 kJ/mol (bond dissociation energy of F2)

F(g) + e- → F-(g) ΔEA = -328 kJ/mol (electron affinity of F)

Li+(g) + F-(g) → LiF(s) ΔHlattice = -??

Using Hess's law:

ΔHlattice = -[ΔHsubl + ΔHIE1 + 0.5ΔHbond + ΔEA]

Plugging in the given values:

ΔHlattice = -[161 + 520 + 0.5(159) - 328] = -1047 kJ/mol

Therefore, the correct choice is B.

Calculate the Lattice Energy for LiF(s) Given the Following