We are being asked to calculate for the heat of solution of lithium iodide using its lattice energy and heat of hydration.
Lattice energy represents the energy released when 1 mole of an ionic crystal is formed from its gaseous ions.
The heat of hydration of an ion is the amount of heat released when one mole of that ion dissolves in water.
The heat of solution, enthalpy change related to the dissolution of a substance in a solvent. It will be composed of the process - bonds being broken and bonds being formed.
The equation below relates the lattice energy, heat of solution, and heat of hydration: