The 14 Types of Major Chemical Reactions

The Types of chemical reactions Can be classified in relation to energy, speed, type of alteration, particles that have been modified and direction.

A chemical reaction as such represents an atomic or molecular transformation that can occur in a liquid, solid or gaseous medium. In turn, this exchange may involve a reconfiguration in terms of physical properties, such as creating a solid, color change, release or absorption of heat, generation of gases, among other processes.

The world around us is made up of a variety of elements, substances and particles that constantly interact with one another. These changes in matter or in the physical state of things are fundamental to the processes that govern mankind. Knowing them is an important part of understanding their dynamics and their influence.

The substances that act in this chemical change or chemical phenomenon are denominated like reactantes or reagents and they generate another class of compounds that differ from the original, called products. They are represented in equations that go from left to right by an arrow that indicates the direction in which the reaction happens.

To better understand how the great diversity of chemical phenomena behaves, it has been necessary to classify them according to specific criteria. A traditional way of encompassing them is as follows: in relation to energy, speed, type of alteration, particles that have been modified and direction.

Types of Chemical Reactions

Energy exchange

This section illustrates the chemical reactions that have been cataloged taking into account the release or absorption of heat. This kind of energy transformation is divided into two classes:

• Exothermic . This type of reactions may include others, as they involve the release of energy or enthalpy. It is observed in the burning of fuels, since the redistribution of the bonds can generate light, sound, electricity or heat. Although they require heat for the break, the combination of elements causes more energy.

• Endothermic . This kind of chemical reaction is distinguished by the absorption of energy. This contribution of heat is necessary to break the bonds and get the desired product. In some cases, the ambient temperature is not sufficient, so it is necessary to heat the mixture.

Kinetic Reactions

Although the concept of kinetics is related to movement, in this context it tells us the speed at which the transformation occurs. In this sense, the types of reactions are as follows:

• Slow . Such reactions can last for hours or even years because of the type of interaction between the various components.
• Fast . They usually happen very quickly, from a few thousandths of a second to a few minutes.

Chemical kinetics is the area that studies the speed of chemical reactions within various systems or media. This kind of transformations can be altered by a great variety of factors, among which we can highlight the following:

• Concentration of reagents . As long as there is a higher concentration of these, the faster the reaction. Since most chemical changes occur in solution, molarity is used. To cause the molecules to collide with one another, it is important to determine the concentration of moles and the size of the vessel.
• The temperature involved . As the temperature of the process increases, the reaction becomes more rapid. This acceleration causes an activation, which in turn allows breaking the links. It is undoubtedly the most preponderant factor in this sense, therefore the laws of speed are subject to its presence or absence.
• Presence of a catalyst . When catalytic substances are used, most molecular transformations occur at a faster rate. In addition, catalysts work both as products as well as reagents, so a small dose is sufficient to drive the process. The detail is that each reaction requires a specific catalyst.
• Surface area of ​​catalysts or reagents . Substances which experience in the solid phase an increase in surface area, tend to be carried out more quickly. This implies that a number of pieces act more slowly than the same amount of fine powder. For this reason, the catalysts are applied to said composition.

Direction of the reaction

Reactions happen in a certain sense depending on the equation that indicates how the transformation of the elements involved will happen. Certain chemical changes tend to occur in a single direction or both at the same time. Following this idea, there are two types of chemical phenomena that can happen:

• Irreversible reactions . In this type of transformation the product can no longer return to its initial state. In other words, substances that come into contact and give off vapors or are precipitated, remain altered. In this case, the reaction takes place from reagents to products.
• Irreversible reactions . Unlike the above concept, the substances that come in contact forming a compound, can return to the initial state. For this to happen, a catalyst or the presence of heat is often required. In this case, the reaction takes place from products to reagents.

Modification of the particles

In this category the predominant principle is the exchange at the molecular level to form compounds that exhibit another nature. Therefore, the reactions involved are named as follows:

• Synthesis or combination . This scenario involves two or more substances that when combined generate a different and more complex product. It is usually represented as follows: A + B → AB. There is a differentiation as to the denomination, since in the combination they can be any two elements, whereas the synthesis requires pure elements.
• Decomposition . As its name indicates, during this chemical change the product generated is divided into 2 or more substances that are simpler. Using its representation, it can be observed as follows: AB → A + B. In summary, a reactant is used to obtain several products.
• Of displacement or substitution . In this type of reaction exists the replacement of an element or atom for another more reactive in a compound. This is applied to create a simpler new product by displacing an atom. The representation as an equation can be seen as: A + BC → AC + B
• Double replacement or displacement . Emulating the previous chemical phenomenon, in this case there are two compounds that exchange atoms to produce two new substances. These usually occur in an aqueous medium with ionic compounds, which generates precipitation, gas or water. The equation looks like this: AB + CD → AD + CB.

Particle Transfer

Chemical reactions represent several phenomena of exchange, especially at the molecular level. When an ion or an electron is transferred or absorbed between two different substances, it gives rise to another class of transformations that are properly cataloged.

Precipitation

During this type of reaction, the ions are exchanged between the compounds. It usually occurs in an aqueous medium with the presence of ionic substances. Once the process starts, an anion and a cation are brought together, which generates an insoluble compound. Precipitation leads to the creation of solid state products.

Acid-base reaction (protons)

Based on the Arrhenius theory by its didactic nature, an acid is a substance that releases a proton. On the other hand, a base is also capable of yielding hydroxide-like ions. This implies that the acidic substances are combined with an hydroxyl to form water and the surplus ions will form a salt. It is also known as the neutralization reaction.

Oxidation-reduction or redox reaction (electrons)

This kind of chemical change is characterized by the verification in the transfer of electrons between the reactants. This finding is observable by the oxidation number. In case there is an electron gain, the number will decrease and so it is understood that it has been reduced. On the other hand, if the number increases, it is considered as an oxidation.

Combustiones

Related to the above, these processes of exchange are distinguished by substances that are oxidized (fuels) and those that are reduced (oxidising). Such interaction releases a large amount of energy, which in turn forms gases. A classic example is the combustion of hydrocarbons, in which carbon is converted to carbon dioxide and hydrogen into water.

Other important reactions

Breathing

This essential chemical reaction for life, occurs at the cellular level. It involves the exothermic oxidation of certain organic compounds to generate energy, which must be used to carry out the metabolic processes.

Photosynthesis

In this case, it refers to a well-known process that run plants to extract organic matter from sunlight, water and salts. The principle lies in the transformation of solar energy into chemical energy, which accumulates in ATP cells, which are responsible for synthesizing organic compounds.

Acid rain

The by-products generated by the various kinds of industries in conjunction with the generation of electricity produce sulfur and nitrogen oxides that end up in the atmosphere. Either by an oxidation effect in the air or by direct emission, the SO ₃ and not ₂ , Which in contact with moisture, form nitric acid and sulfuric acid.

Greenhouse effect

The small proportion of CO ₂ In the Earth's atmosphere is responsible for maintaining a constant temperature of the planet. As this gas accumulates in the atmosphere, it generates a greenhouse effect that heats the earth. Although it is a necessary process, its alteration brings unexpected climatic changes.

Aerobic and Anaerobic Reactions

When the concept of aerobic is related, it implies that within the transformation the presence of oxygen will be necessary for the reaction to occur. Otherwise, when there is an absence of oxygen during the process, it is considered as an anaerobic event.

In simpler terms, during an aerobic workout that require a prolonged time, energy is obtained through the oxygen that is breathed. This element is incorporated to the muscles through the blood, which produces a chemical exchange with the nutrients, which will generate energy.

Conversely, when the exercise performed is of anaerobic nature, the energy required is for a short period of time. To obtain it, carbohydrates and fats undergo chemical decomposition, which produces the required energy. In this case, the reaction does not require the presence of oxygen for the process to function properly.

Influential Factors in Chemical Reactions

Like any process that is framed within a context of manipulation, the environment plays a fundamental role as well as other factors related to chemical phenomena. In addition to accelerating, decelerating or provoking the desired reaction, recreating the ideal conditions requires controlling all the variables that could alter the desired result.

One of those factors is light, which is essential for certain types of chemical reactions, such as those of dissociation. Not only does it work as a trigger, it can also have an adverse effect on some substances, such as acids, whose exposure degrades them. Due to this photosensitivity, they are protected by dark containers.

Likewise, electricity expressed as current with a specific charge can enable the dissociation of different substances, especially those that are dissolved in water. This generates a chemical phenomenon known as electrolysis, which is also present in the combination of some gases.

Related to the aqueous medium, moisture contains qualities that allow it to act both as acid as well as base, which allows altering its composition. This facilitates chemical changes by operating as a solvent or facilitating the incorporation of electricity during the reaction.

Within organic chemistry, ferments play a major role in generating important effects related to chemical reactions. These organic substances allow the combination, dissociation and interaction between various compounds. Fermentation is essentially a process that occurs between elements of an organic nature.

References

1. Restrepo, Javier F. (2015). Fourth period. Chemical reactions and stoichiometry. Web: es.slideshare.net.
2. Osorio Giraldo, Darío R. (2015). Types of chemical reactions. Faculty of Exact and Natural Sciences. University of Antioquia. Web: aprendeenlinea.udea.edu.co.
3. Gómez Quintero, Claudia S. Notes on chemical processes for systems engineering. Chap. 7, Reaction kinetics and chemical reactors. University of the Andes. Web: webdelprofesor.ula.ve.
4. Online teacher (2015). Chemical changes in matter. Web: www.profesorenlinea.com.
5. Martínez José (2013). Endothermic and exothermic reactions. Web: es.slideshare.net.
6. Extract (without author and date). Chemical reactions. 1st of Bachillerato. Web: recursostic.educación.es.