Lithium iodide has a lattice energy of -7.3 ×10^2 kJ / mol and a heat of hydration of -793 kJ

step 1 So lithium iodide has a lattice energy of negative 7 .3 times 10 to a pair of 2 kilojoules per m

Lithium iodide has a lattice energy of -7.3 ×10^2 kJ / mol...

Lithium iodide has a lattice energy of $-7.3 \times 10^{2} \mathrm{~kJ} / \mathrm{mol}$ and a heat of hydration of $-793 \mathrm{~kJ} / \mathrm{mol}$. Find the heat of solution for lithium iodide and determine how much heat is evolved or absorbed when $15.0 \mathrm{~g}$ of lithium iodide completely dissolves in water.

Key Concepts

Stoichiometry and Thermochemical Calculations

Stoichiometry involves using the molar relationships in a chemical process to calculate the total energy change for a given mass of a compound. In thermochemical calculations, the heat of solution per mole is applied alongside the molar mass of the solute to determine the total heat evolved or absorbed when a specific amount of the substance dissolves.

Heat of Solution

Heat of solution is the overall enthalpy change for the process of dissolving a substance in a solvent. It is determined by the combination of the energy required to break the ionic lattice (lattice energy) and the energy released upon hydration of the ions (enthalpy of hydration). Calculating the heat of solution helps predict whether heat will be absorbed or released during the dissolution process.

Lattice Energy

Lattice energy is the energy released when ions in the gas phase come together to form a crystalline ionic solid. It reflects the strength of the ionic bonds in the solid and is typically expressed as a negative value because energy is released when the lattice forms. This concept is crucial for understanding the stability of ionic compounds and how much energy is needed to break the ionic lattice during dissolution.

Enthalpy of Hydration

Enthalpy of hydration is the energy change that occurs when one mole of gaseous ions is surrounded by water molecules to form hydrated ions. This process releases energy, as indicated by a negative enthalpy, and is a key factor in the dissolution process of ionic compounds, as it counterbalances the energy required to overcome the lattice energy.

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