- A chemical solution is a homogeneous mixture formed by the complete dissolution of a solute in a solvent, giving rise to a uniform combination of substances at the molecular level.
The solute is the substance that dissolves in a solution, and the solvent is the medium in which the solute dissolves. This phenomenon is possible due to the interaction between the solute molecules and the solvent molecules, which break the intermolecular forces and allow the mixing of both substances.
Types of chemical solutions
Chemical solutions can be classified in various ways, depending on different criteria.
Below are some of the most common classifications:
Depending on the aggregation status
According to the state of aggregation, solutions are classified as gaseous, liquid and solid:
- Gaseous solutions: The solute and solvent are both gases. For example, air.
- Liquid solutions: The solute is dissolved in a liquid solvent. A common example is water dissolving salt.
- Solid solutions: Both the solute and the solvent are solids. Bronze, an alloy of tin and copper, is an example.
Depending on the solvent
Depending on the solvent, solutions can be aqueous or non-aqueous.
- Aqueous solutions: Water is the solvent.
- Non-aqueous solutions: Other solvents that are not water.
Depending on the amount of solute
Solutions can also be classified according to the amount of solute present relative to the amount of solvent.
- Dilute solutions: They contain a low concentration of solute.
- Concentrated solutions: They contain a high concentration of solute.
- The concentration of a solution can be expressed in a variety of ways, such as mass percent, volume percent, or molarity, providing different perspectives on the composition of the mixture.
Depending on the type of solutes
Depending on the type of solute used in a chemical solution, we distinguish electrolytic and non-electrolytic solutions:
- Electrolyte solutions: Electrolyte solutions contain solutes that, when dissolved in the solvent, dissociate into ions. This dissociation process allows for a high concentration of ions in the solution, which in turn facilitates the conduction of electricity.
- Non-electrolyte solutions: Non-electrolyte solutions contain solutes that do not dissociate into ions when dissolved in the solvent. In these solutions, there is little or no conduction of electricity, since the absence of free ions limits the solution's ability to transport electrical charge.
Depending on temperature and solubility
Generally solubility increases with increasing temperature for many substances, although exceptions exist.
Saturation of a chemical solution is a phenomenon that occurs when the maximum amount of solute that can dissolve in a particular solvent at a specific temperature is reached.
- Unsaturated solutions: Contain less solute than could dissolve at a specific temperature.
- Saturated solutions: They contain the maximum amount of solute that can dissolve at a given temperature. Any additional solutes added will not dissolve and will settle to the bottom of the solution.
- Supersaturated solutions: Contain more solute than would normally dissolve at a given temperature. Supersaturation is the chemical principle that causes crystallization.
According to the homogeneity
Depending on the homogeneity we can classify the solutions into these two types:
- Homogeneous solutions: In these solutions, the substances that make up the solute and solvent are completely mixed at the molecular level, resulting in a uniform mixture. The properties of the solution are the same anywhere in the sample.
- Suspensions: In suspensions, the solute particles do not completely dissolve in the solvent and are therefore visible. These particles tend to settle over time due to gravity, leading to phase separation. The suspensions are not homogeneous and may require agitation to keep them uniform for a short period.
Depending on the nature of the dissolved particles
- Molecular solutions: In molecular solutions, the dissolved particles are individual molecules that maintain their original molecular structure. There is no significant dissociation of the molecules into ions when the solute is dissolved in the solvent.
- Ionic solutions: Dissolved particles are ions, which means that the dissolved substances have dissociated into positive and negative ions when dissolved in water. This process is commonly observed with ionic compounds, such as salts. For example, when sodium chloride (NaCl) is dissolved in water, it dissociates into sodium (Na⁺) and chloride (Cl⁻) ions.
According to Ideality
- Ideal Solutions: They follow the laws of ideal solutions, where the interaction between the molecules of the solute and the solvent follows a predictable behavior.
- Non-Ideal Solutions: They deviate from the expected behavior according to the laws of ideal solutions.
Examples
A common example is saline solution used in medicine. This aqueous solution of sodium chloride (NaCl) has a specific concentration to maintain electrolyte balance in the body and is commonly used in intravenous treatments and eye washes.
In the domestic sphere, carbonated drinks are examples of aqueous solutions. These contain carbon dioxide dissolved in water under pressure, providing the characteristic effervescence when released. Additionally, detergent solutions used for washing dishes or clothes are mixtures designed to dissolve and remove grease and dirt.
In the industrial field: chemical solutions are essential in processes such as the manufacturing of pharmaceutical products.
Finally, the air we breathe is a gaseous solution made up of a mixture of nitrogen, oxygen, carbon dioxide and other gases.