Solutions and Solubility Notes

A solution is defined as a homogeneous mixture consisting of one or more solutes dissolved in a solvent.
For example, to create a salt solution, one can add salt to a glass of water and mix it until the salt completely dissolves.
It is important to note that there is a limit to how much salt can dissolve in water, beyond which no more salt will dissolve. This limit is referred to as solubility.

Definition: The solubility of a substance is the maximum amount of the substance that can be dissolved in a specific amount of a certain solvent at a fixed temperature.

Three key factors that influence the solubility of a substance include:
- The solvent: A solute may exhibit high solubility in water but very low solubility in hexane.
- Temperature: Increasing the temperature typically increases solubility.
- Amount of solvent: A greater amount of solvent allows for more solute to dissolve.
Each substance has its own distinct solubility (e.g., the solubility of salt differs from that of sugar).

Solubility can be expressed in multiple ways:
- One common method is to state the mass of solute that can be dissolved in a given volume of solvent, such as 32 g per 100 mL or 424 g/L.
- The most familiar method is by stating the mass of solute that can be dissolved in 100 g of solvent; for example, 27 g per 100 g of water.

Various terms are used to describe the solubility of a substance in a given solvent:
- Soluble: A substance is classified as soluble if it readily dissolves in that solvent (e.g., sodium chloride is soluble in water).
- Sparingly soluble: A substance shows limited solubility in that solvent (e.g., iodine is sparingly soluble in water).
- Insoluble: A substance is deemed insoluble if it does not dissolve in that solvent (e.g., sodium chloride is insoluble in ethanol).

Common terminology used to describe solutions includes:
- Concentrated: A concentrated solution contains a relatively large amount of solute dissolved in the solvent.
- Dilute: A dilute solution consists of a small amount of solute dissolved in the solvent.
- Saturated: A saturated solution is one where the maximum amount of solute has dissolved in the solvent at a specific temperature. Adding more solute will result in undissolved solid.
- Supersaturated: A supersaturated solution has more solute than the theoretical maximum amount it can hold at that temperature. Disturbances in the solution prompt the excess solute to precipitate, crystallize, or fall out of the solution.

Since temperature affects solubility, one can graph solubility against temperature for a particular solute dissolved in a specified solvent. This graph is referred to as a solubility curve.
By analyzing a solubility curve, deductions can be made regarding how much solute dissolves at various temperatures.