Use the Born–Haber cycle and data from Appendix IIB, Chapter 9 and this chapter to calculate the lattice energy of KCl. (ΔHsub for potassium is 89.0 kJ>mol.)

Key Concepts

Born-Haber Cycle

The Born-Haber cycle is a thermodynamic cycle that relates the lattice energy of an ionic compound to other thermodynamic quantities. It involves several steps, including the sublimation of the metal, ionization energy, electron affinity, and the formation of the ionic solid from gaseous ions. This cycle allows for the calculation of lattice energy by applying Hess's law, which states that the total enthalpy change is the sum of the changes in each step.

Lattice Energy

Lattice energy is the energy released when gaseous ions combine to form an ionic solid. It is a measure of the strength of the forces between the ions in the solid lattice structure. A higher lattice energy indicates a more stable ionic compound, as it reflects stronger ionic bonds. Lattice energy can be calculated using the Born-Haber cycle, which incorporates various energy changes associated with the formation of the ionic compound.

Thermodynamic Data

Thermodynamic data, such as enthalpy of sublimation, ionization energy, and electron affinity, are essential for performing calculations in the Born-Haber cycle. These values provide the necessary energy changes that occur during the formation of ionic compounds. For example, the enthalpy of sublimation for potassium (ΔHsub) indicates the energy required to convert solid potassium into gaseous atoms, which is a crucial step in determining the lattice energy of KCl.