The main types of chemical reactions are:
Acid-Base Reactions Oxidation-Reduction Reactions Combustion Reactions Displacement Reactions Double Displacement Reactions Acid-Metal Reactions Combination Reactions Decomposition Reactions
A chemical reaction is the process of arrangement of atoms between substances to form new compounds with different properties. That is, when compounds or elements react, they are transformed into one or more different substances.
For example, when paper is burned, oxygen from the air and the cellulose in the paper react, turning into carbon dioxide and water vapor.
The substances that react are called reactants and the substances that are generated are called products. The chemical reaction is represented by a chemical equation, where the reactants are placed to the left of an arrow followed by the products to the right, like this:
Reactants→Products
A nuclear reaction is not a chemical reaction, since the transformation of atoms into another type of atom occurs. For example, in the fission of uranium, krypton and barium are formed, while mass is lost in the form of energy. Neither are chemical reactions the dissolution of a substance in water or the ionization of a compound, as well as the change of state of a material.
Here we present the main types of chemical reactions with examples.
1. Acid-base reactions
Also called neutralization reactions, the reaction of an acid with a base occurs. The acid contributes H+ ions and the base contributes OH- ions to form water H2O, at the same time that a salt is formed.
For example, when hydrochloric acid HCl reacts with sodium hydroxide NaOH, the products are water H2O and the sodium chloride salt NaCl:
You may also be interested in seeing Acids and bases.
2. Oxidation-reduction reactions
They are a type of chemical reaction where the reactants gain or give up electrons to each other. When they gain electrons they are reduced, when they give up electrons they are oxidized. The oxidation and reduction reactions are simultaneous.
For example, for the extraction of iron in mines, iron oxide III Fe2O3 is reduced by the action of carbon monoxide CO which is oxidized. The products are iron in its element form Fe and carbon dioxide CO2:
You may also be interested in seeing Oxidation and reduction.
3. Combustion reactions
In combustion reactions, oxygen combines with organic compounds, made up of carbon, hydrogen, and oxygen. The final product is carbon dioxide and water.
An example of a combustion reaction is the one that occurs when methane CH4 or cooking gas is burned:
You may also be interested in seeing Organic and inorganic compounds.
4. Displacement reactions
In this type of reaction, one element replaces another in a compound. Such is the case for the reaction between sodium Na and zinc iodide ZnI2, where sodium displaces zinc to form sodium iodide NaI:
5. Double Displacement Reactions
This reaction occurs in solution when the reactants ionize in such a way that an ion exchange occurs. If the combination produces a compound that precipitates by forming an insoluble salt, we have a precipitation reaction.
For example, when the salts of barium nitrate Ba(NO3)2 and potassium sulfate K2SO4 react, ions are exchanged to produce potassium nitrate KNO3 and barium sulfate BaSO4, which is insoluble in water and precipitates:
6. Acid-metal reactions
An acid such as hydrochloric acid HCl and a metal can react to form a salt and hydrogen gas H2:
7. Combination reactions
Elements or compounds combine to form a different product. For example, sulfur dioxide SO2 combines with oxygen O2 to form sulfur trioxide SO3:
8. Decomposition reactions
A simple compound gives rise to two or more products. An example of decomposition is the electrolysis process, that is, when an electric current is passed through water, it breaks down into hydrogen H2 and oxygen gas:
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References
Ahtee, M., Varjola, I. (2007) Students’ understanding of chemical reaction. International Journal of Science Education. 20: 305-316. DOI:10.1080/0950069980200304
Commons, C., Commons, P (editors) (2020). Heinemann Chemistry 1, 5th ed. Pearson Australia. Melbourne.
Rosenberg, JL, Epstein, LM, Krieger, PJ (2007) Schaum’s outlines College Chemistry 9th ed. McGraw-Hill. Toronto.