Use the Born-Haber cycle to calculate the lattice energy of NaBr(s) given the following data: $\Delta$ H(sublimation) Na = 109 kJ/mol
I₁ (Na) = 496 kJ/mol
Bond energy (Br-Br) = 192 kJ/mol
EA (Br) = 324 kJ/mol
$\Delta$ H_f (NaBr(s) ) = -361 kJ/mol

Question

Use the Born-Haber cycle to calculate the lattice energy of NaBr(s) given the following data:

\Delta

H(sublimation) Na = 109 kJ/mol
I₁ (Na) = 496 kJ/mol
Bond energy (Br-Br) = 192 kJ/mol
EA (Br) = 324 kJ/mol

\Delta

H_f (NaBr(s) ) = -361 kJ/mol

Quizplus · Accepted Answer

The lattice energy of NaBr(s) is the energy required to separate the ions in NaBr(s) into gaseous ions. The Born-Haber cycle is a thermodynamic cycle that can be used to calculate the lattice energy of an ionic compound. The Born-Haber cycle for NaBr(s) is:Na(s) → Na(g)      ΔH = 109 kJ/molNa(g) → Na+(g) + e-      ΔH = 496 kJ/mol1/2 Br2(g) → Br(g)      ΔH = 192 kJ/molBr(g) + e- → Br-(g)      ΔH = -324 kJ/molNa+(g) + Br-(g) → NaBr(s)      ΔH = -361 kJ/molThe lattice energy of NaBr(s) is the sum of the enthalpies of the steps in the Born-Haber cycle:ΔHlattice = ΔH(sublimation) Na + I1 (Na) + 1/2 Bond energy (Br-Br) + EA (Br) + ΔHf (NaBr(s))ΔHlattice = 109 kJ/mol + 496 kJ/mol + 1/2 (192 kJ/mol) + (-324 kJ/mol) + (-361 kJ/mol)ΔHlattice = 738 kJ/molTherefore, the lattice energy of NaBr(s) is 738 kJ/mol.

Use the Born-Haber Cycle to Calculate the Lattice Energy of NaBr(s)