Consider the following: Li(s)+(1)/(2) I2(g) →LiI(s) ΔH=-292 kJ . LiI(s) has a lattice energy of

step 1 considering the following reaction of LI, add half -I2, gives us lithium iodide. So we have a de

Consider the following: Li(s)+(1)/(2) I2(g) →LiI(s) ΔH=-292...

Consider the following: $\operatorname{Li}(s)+\frac{1}{2} \mathrm{I}_{2}(g) \rightarrow \operatorname{LiI}(s) \Delta H=$$-292 \mathrm{kJ} .$ LiI(s) has a lattice energy of $-753 \mathrm{kJ} / \mathrm{mol} .$ The ionization energy of $\operatorname{Li}(g)$ is $520 . \mathrm{kJ} / \mathrm{mol}$, the bond energy of $\mathrm{I}_{2}(g)$ is $151 \mathrm{kJ} / \mathrm{mol},$ and the electron affinity of $\mathrm{I}(g)$ is $-295 \mathrm{kJ} / \mathrm{mol} .$ Use these data to determine the heat of sublimation of Li(s).

Key Concepts

Born–Haber Cycle

The Born–Haber cycle is a thermochemical cycle that relates the lattice energy of an ionic solid to other steps in the formation of the compound, such as sublimation, ionization, bond dissociation, and electron affinity. It provides a systematic way to calculate lattice energy by considering the energy changes for each process, ensuring that the overall enthalpy change of formation is consistent with Hess’s law.

Sublimation Energy

Sublimation energy is the energy required to convert a substance from its solid phase directly to its gaseous phase. In the context of forming an ionic compound, sublimation energy is the energy needed to vaporize the metal element, which is the first step in the Born–Haber cycle for creating gaseous metal atoms before ionization.

Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom to form a cation. It is a crucial step in the Born–Haber cycle, as the removal of an electron from the neutral metal atom forms the positively charged ion necessary for ionic bonding.

Electron Affinity

Electron affinity is the energy change that occurs when a neutral gaseous atom gains an electron to form a negative ion. In the formation of ionic compounds, the electron affinity is critical because it contributes to the energy change associated with the formation of the anion in the Born–Haber cycle.

Bond Dissociation Energy

Bond dissociation energy is the energy required to break the bonds in a molecule to form individual atoms. For diatomic molecules like I2, this energy is needed to generate individual atoms before one can undergo the electron affinity process, making it an essential part of the cycle for forming the necessary ions.

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