7 junio, 2024

Chemical solutions: concept, characteristics, types, examples

We explain what chemical solutions are, their characteristics, the types that exist and we give several examples.

What are chemical solutions?

The chemical solutions are homogeneous mixtures between a solvent and one or more solutes. The simplest solutions are made up of a single solute and a solvent, like when we dissolve sugar in water, but there are solutions that can become very complex with hundreds of solutes.

Most common solutions are in the liquid state, and in most of these cases the solvent is water. For this reason, water is often called «the universal solvent.» But the solutions are not limited to liquids, since there are solutions in the gaseous state and in the solid state.

The solute can also be in different states. For example, you can have liquid solutions with solid (like salt), liquid (like alcohol), or gaseous (like carbon dioxide in soft drinks) solutes.

How to recognize the solute and the solvent?

In any solution in which there is water, this is considered to be the solvent. In all other cases, the solvent corresponds to the component that is found in greater quantity or in greater proportion and is almost always a liquid. The other components present in the solution are considered solutes.

Let’s see two examples:

In a sugar-water solution, water is the solvent and sugar is the solute. The isopropyl alcohol that we buy at the pharmacy is a solution made up of water and alcohol. In this solution the solvent is water despite being in a smaller proportion than alcohol.

Characteristics and properties of chemical solutions

They are homogeneous mixtures

Solutions are mixtures in which the solute is indistinguishable from the solvent, neither with the naked eye nor with the use of a magnifying glass or microscope.

have uniform composition

This means that any portion of a solution will always have the same components (solute and solvent) at the same concentration.

They are characterized by their concentration

Concentration is one of the most important characteristics of a solution, since it determines many of its properties.

They are translucent (transparent)

Liquid solutions must be translucent, meaning that light must be able to pass through them without scattering.

are stable

A solution in which the solute and solvent do not react with each other will be stable indefinitely. This means that it will not undergo any change over time, as long as its composition remains constant (the solvent does not evaporate, for example).

Its physical and chemical properties are different from those of the solvent.

The physical and chemical properties of the solvent change as it mixes with the solute. For example, solutions have a higher boiling point, a lower melting point, and also have a high osmotic pressure compared to the pure solvent.

They can be separated by some physical and chemical processes

Solutions cannot be separated by filtration, centrifugation, or decantation. They can only be separated by physical or chemical methods such as crystallization, distillation, evaporation, reverse osmosis, and chromatography, among others.

Types of chemical solutions

Chemical solutions can be classified according to their concentration, according to their physical state and according to the nature of the solvent:

According to your concentration

unsaturated solutions: are those in which the solute has not yet reached its maximum concentration in the solvent. Because of this, still more solute can be dissolved to make a more concentrated solution.
saturated solutions: are solutions in which the solvent can no longer dissolve more solute. In these cases there is always a part of the solute undissolved. For example, if we add a lot of salt to a glass of water, some of this salt will not dissolve and will remain at the bottom of the glass.
supersaturated solutions: are solutions in which there is more dissolved solute than the solvent admits. This can be accomplished by heating a saturated solution to dissolve even more solute, then slowly allowing it to cool to the initial temperature. These solutions are unstable, since any disturbance such as a vibration or a small dust particle on the surface can cause excess solute to separate.

According to your physical state

liquid solutions: are the most common. In this type of solution the solvent is a liquid (such as water, alcohol, oil, etc.) but the solute can be in any state (solid, liquid or gas). Some examples of liquid solutions are salt water, wine, and soft drinks.
solid solutions: In these cases, both the solvent and the solute are in the solid state. The most common examples of this type of solution are metal alloys such as bronze, steel and brass, but there are also other examples such as glass.
gaseous solutions: As their name indicates, they are homogeneous mixtures in which all the components are in a gaseous state.

According to the solvent

aqueous solutions: If the solvent in a solution is water, then it is said to be an aqueous solution. These are the most common solutions that can be found in daily life.
alcoholic solutions: The most common solvent, after water, is alcohol. Common alcohols include methanol, ethanol, and isopropyl alcohol.
Solutions in other organic solvents: There are many other organic compounds that are used as solvents. These include some alkanes, most ethers, liquid ketones, and others.

Examples of Chemical Solutions

Lemonade

It is an aqueous solution made up of water as the solvent and lemon juice and sugar as the solutes.

Seawater

Sea water or salt water is an aqueous solution made up of water and a mixture of salts. Among these salts, the one found in the highest proportion is sodium chloride (NaCl) known as common table salt.

concentrated syrup

This is an almost saturated aqueous solution of sugar water.

Carbonated water

Carbonated water, also known as soda, is an aqueous solution of carbon dioxide gas (CO2) in water.

Air

Air is a gaseous solution in which nitrogen can be considered as a solvent and oxygen and the other gases as solutes.

Clarified butter

By melting the butter and removing all the foam, you get a clear yellow solution called clarified butter. This is a solution in which both the solvent and the solutes are fats.

stained glass

Colored glasses are solid-state solutions, in which the solvent is molten silica and the solutes are other minerals that give the glass its characteristic color.

Coffee

This is a complex aqueous solution that contains many solutes (including caffeine) that give the beverage its characteristic aroma and flavor.

The steel

Steel is an alloy or solid solution made up of metallic iron and graphite carbon.

blood plasma

Blood plasma is a solution obtained after centrifuging the blood to remove all cells and other suspended solids. This is a fairly concentrated aqueous solution that contains hundreds of solutes including carbohydrates, amino acids, soluble proteins, and electrolytes, among others.

References

Chang, R. and Goldsby, K. (2014). Chemistry. 11th ed. New York: McGraw-Hill Education. Solution (January 25, 2021). On Wikipedia.org. Brown, T.L., LeMay, E. (2018). Chemistry: The Central Science. 14th Edition. pearson. Krestonosich, S., et al. (1992). Solutions. Editorial Miró. Vidal, JA (Editor) (1997). Interactive Mentor – Student Thematic Encyclopedia. Editorial Ocean. Barcelona.

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