Final answer:
The lattice energy of rubidium iodide (RbI) can be calculated using the Born-Haber cycle, accounting for the ionic charges and internuclear distance. The formula RbI indicates ions with charges of −1 and −1, leading to a lower lattice energy compared to compounds with ions of higher charges.
Step-by-step explanation:
The calculation of the lattice energy of rubidium iodide (RbI) involves estimating the energy released when gaseous ions form an ionic solid. The Born-Haber cycle is a common method for calculating lattice energy, which is a process that includes several steps such as sublimation, ionization, and electron affinity, as well as the energy released when the ionic solid forms. This method uses Hess's Law to break down the formation of an ionic compound into these individual steps.
Using the Born-Haber cycle, we know that the lattice energy is directly proportional to the product of the ionic charges and inversely related to the internuclear distance. As rubidium iodide has a cubic unit cell with iodide ions at the corners and a rubidium ion at the center, forming a simple cubic lattice, its formula unit RbI indicates ions with charges of −1 and −1. From this, along with known enthalpies for sublimation, ionization, and electron affinity, and the internuclear distance, we can estimate the lattice energy for RbI.
While the direct calculation involves complex equations and exact values for each enthalpy change, the general concept is that a higher product of the ionic charges and a smaller internuclear distance will result in a larger lattice energy. Since RbI involves −1 and −1 ions, its lattice energy would be comparatively lower than a compound with ions having higher charges, according to the principle that lattice energy is directly proportional to the charges of the ions involved.