Consider two ionic solids, both composed of singly charged ions, that have different lattice energies. (a) Will the solids have the same solubility in water? (b) If not, which solid will be more soluble in water, the one with the larger lattice energy or the one with the smaller lattice energy? Assume that solute–solvent interactions are the same for both solids. [Section 13.1]

Verified step by step guidance

1. Understand that lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions.
2. Recognize that a higher lattice energy indicates stronger ionic bonds within the solid, making it more stable and less likely to dissolve.
3. Recall that solubility in water involves breaking the ionic bonds in the solid and forming new interactions between the ions and water molecules.
4. Consider that a solid with a smaller lattice energy will require less energy to break apart, making it more soluble in water.
5. Conclude that, assuming solute–solvent interactions are the same, the solid with the smaller lattice energy will be more soluble in water.

Key Concepts

Lattice Energy

Lattice energy is the amount of 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. Higher lattice energy indicates stronger ionic bonds, which typically results in lower solubility in water, as more energy is required to break these bonds during dissolution.

Solubility

Solubility refers to the ability of a substance to dissolve in a solvent, forming a homogeneous solution. In the context of ionic solids, solubility is influenced by the balance between lattice energy and the energy of solute-solvent interactions. A solid with lower lattice energy is generally more soluble because it requires less energy to separate the ions from the solid structure.

Solute-Solvent Interactions

Solute-solvent interactions are the attractive forces between the solute particles and the solvent molecules. In the case of ionic solids dissolving in water, these interactions involve ion-dipole forces, where water molecules surround and stabilize the ions. If solute-solvent interactions are strong enough to overcome the lattice energy, the solid will dissolve more readily.