Solubility and Solubility Curves

Solubility refers to the maximum amount of a solute that can be dissolved in a certain amount of solvent at a specified temperature.
The solute is the substance that is being dissolved, usually in lesser quantity, and the solvent is the substance doing the dissolving, usually in greater quantity.
If a solution can no longer dissolve more solute at a given temperature, it is termed “saturated.” If it can still dissolve more, it is “unsaturated.”
A solute’s solubility can be affected by changes in temperature. For most solid solutes, solubility increases as the temperature rises. However, for gases, solubility decreases with an increase in temperature.
A solution that contains more solute than it would normally be able to dissolve at a given temperature is labelled a “supersaturated” solution. This is usually achieved through cooling a saturated solution.
Solubility curves plot the amount of solute that can be dissolved in 100g of water against the temperature. They help predict how much solute could be dissolved at any given temperature.
The curve shows that the solubility of most solids increase with temperature. The point on the curve for any given temperature shows the maximum amount of solute that can be dissolved at that temperature.
If a particular amount of solute at a specific temperature lies above the curve on the graph, it indicates the solution is supersaturated. If it lies on the curve, the solution is saturated. If it lies below the curve, the solution is unsaturated.
The solubility of gases is affected differently by temperature. Unlike solids, gases become less soluble as temperature increases.
It is also important to note that pressure can affect the solubility of gases in liquids. Increasing the pressure increases gas solubility, while reducing the pressure decreases it. This is explained by Henry’s law.
Finally, solubility does not just rely on physical conditions (temperature, pressure), it is also a property determined by the particular combination of solute and solvent. Hence, certain substances may just be insoluble in a particular solvent regardless of the temperature or pressure.
Understanding solubility and solubility curves is essential in predicting the behaviour of different substances in various conditions, which has important implications in a variety of scientific fields, from chemistry to environmental science.