Answer to Question #267515 in General Chemistry for Pato

Question

Consider a hypothetical ionic compound AB (comprised of A⁺ and B^- ions).

Given the following enthalpy data and using a Born-Haber cycle calculation, predict ΔH_lattice in kJ mol^-1.

A_(s) + B_(s) → AB_(s) Δ_rH = -430 kJ mol^-1

A_(s) → A_(g) Δ_rH = 111 kJ mol^-1

B_(s) → B_(g) Δ_rH = 100 kJ mol^-1

First ionization energy of A_(g) = 507 kJ mol^-1

Electron affinity enthalpy of B_(g) (exothermic) = -343 kJ mol^-1

Answer 1

from the Born Haber cycle,

- ΔHf = delta H (sublimation of A) + First ionization energy of A (gas phase) + ΔH (sublimation of B) - Electron affinity of B + ΔHlattice

or

- 421 = 108 + 475 + 118 - 389 + ΔHlattice

or

ΔHlattice = - 733 KJ / mole.