soluble

Soluble is a term used in chemistry to describe a substance's ability to dissolve in a solvent to form a homogeneous solution. A substance that is soluble in a given solvent will disperse at the molecular level, yielding a single phase without separation. Solubility refers to the maximum amount of solute that can dissolve at a specific temperature, producing a saturated solution. Depending on conditions, solutions can be classified as saturated, unsaturated, or supersaturated.

Solubility depends on the nature of the solute and solvent and on the interactions between them, such as ion–dipole interactions, hydrogen bonding, and the lattice energy of the solute. Commonly, solubility is expressed as grams of solute per 100 grams of solvent, or in terms of molarity, molality, or mole fraction. The term is often qualified by the solvent, for example, “soluble in water” or “soluble in ethanol.”

Different substances show different behaviors. In water, many ionic compounds and polar molecules are soluble, while nonpolar compounds are generally soluble in nonpolar solvents. For gases dissolved in liquids, solubility is usually described by Henry’s law, with solubility increasing under higher pressure and typically decreasing with rising temperature. For sparingly soluble salts, solubility is described by solubility products (Ksp), which indicate the extent of dissolution at a given temperature.

Applications of solubility knowledge include chemistry experiments, formulation of medicines to ensure bioavailability, environmental science, and industrial separations. Understanding solubility helps predict which substances will mix, react, or separate under specified conditions.