ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

Lattice energy is specifically defined as the energy required to separate one mole of an ionic solid into its gaseous ions. This definition emphasizes the strong electrostatic forces present in ionic compounds, which hold the cations and anions closely together within a crystal lattice. When these ions are separated, energy must be supplied to overcome these forces, resulting in a positive lattice energy value.

Understanding lattice energy is crucial in the context of ionic compounds since it helps explain their stability and other properties, such as melting points and solubility. The larger the lattice energy, the more stable the ionic compound, as more energy is required to break the ionic interactions.

The other choices do not accurately define lattice energy: the first choice refers to the enthalpy of fusion rather than lattice energy; the third option relates to the overall energy change in a chemical reaction but does not pinpoint the interactions involved in ionic compounds; the last choice discusses energy absorption in a general chemical reaction, which does not apply specifically to the separation of ions in a lattice.