A solution consists of two components – a solute and a solvent. Solubility is the property of a solute to dissolve into a solvent. The solute and the solvent can be either solid, liquid, or gaseous. The IUPAC definition of solubility states that it is the analytical composition of saturated solutions which is expressed in the proportion of the solute and the solvent. With the help of the mole concept, solubility can be expressed in terms of units such as mole fraction and molarity.
Effect of Temperature on Solubility
The solubility of a solute, depending on its nature, may increase or decrease with an increase in temperature. For example, the solubility of most liquids/solids increases with temperature. However, when the critical temperature of liquid water is reached, its dielectric constant decreases. This implies that the polarity of the water would decrease at its critical temperature, thereby reducing the solubility of ionic solutes.
It can be noted that the solubility of organic compounds almost always increases with an increase in temperature. Some solids are purified via recrystallization – a process that exploits the differing solubility of the solid in hot and cold solvents.
Effect of Pressure on Solubility
While considering solids and liquids, the pressure applied has a negligible impact on the solubility of the solute. However, the relationship between pressure and solubility does have practical applications in some fields, such as the precipitation fouling of oil fields with the help of CaSO4 (calcium sulfate).
Thus, solubility is a property of substances which is often expressed in terms of concentration. It can be considered as the maximum amount of solute dissolved in equilibrium with a given amount of solvent. However, several factors can affect the solubility of a substance. Examples include the temperature, pressure, and the common ion effect. To learn more about solubility and other related topics in chemistry, subscribe to the BYJU’S Youtube channel and enable notifications.