Solubility

Water is often referred to as "the universal solvent" because of the number of common substances that dissolve in water. When substances are dissolved in water to the extent that no more will dissolve at that temperature, the solution is said to be saturated. The substance dissolved is called the solute and the dissolving medium is called a solvent. To give an accurate statement of a substance's solubility, three conditions are mentioned: the amount of solute, the amount of solvent, and the temperature of the solution. Since the solubility varies for each substance and for different temperatures, a student must be acquainted with the use of solubility charts.

General Rules of Solubility

All nitrates, acetates, and chlorates are soluble

All common compounds of sodium, potassium, and ammonium are soluble

All chlorides are soluble except those of silver, mercury, and lead

All sulfates are soluble except those of lead, barium, strontium, and calcium

The normal carbonates, phosphates, silicates, and sulfides are insoluble except those of sodium, potassium, and ammonium

All hydroxides are insoluble except those of sodium, potassium, ammonium, calcium, barium, and strontium

Summary of Types of Solutes and Relationship of Type to Solubility

Generally speaking, solutes are most likely to dissolve in solvents with similar characteristics, that is ionic, and polar solutes dissolve in polar solvents and nonpolar solutes dissolve in nonpolar solvents.

It should also be mentioned that polar molecules that do not ionize in aqueous solutions (e.g. sugar, alcohol, glycerol) have molecules as solute particles; polar molecules that partially ionize in aqueous solution (e.g. ammonia, acetic acid) have a mixture of molecules and ions as solute particles; and polar molecules that completely ionize in aqueous solution (e.g. hydrogen chloride and hydrogen iodide) have ions as solute particles.