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Types of Chemical Reactions

Types of Chemical Reactions

This lesson aligns with Next Generation Science Standards (NGSS) PS1.B

Chemical reactions involve breaking chemical bonds between reactant molecules and forming new bonds between product molecules. Changes in color and temperature, formation of gas, formation of a precipitate, production of new odor, etc., all indicate a chemical reaction. Chemical reactions are always happening around us, e.g., cooking, combustion, photosynthesis, etc. Some reactions absorb energy from surroundings to proceed, whereas some reactions evolve energy in the form of heat and create new products. These reactions are named endothermic and exothermic reactions, respectively. This article will discuss types of chemical reactions, synthesis reactions, decomposition reactions, single displacement reactions, double displacement reactions, and combustion reactions. 

Types of Chemical Reactions 
During a chemical reaction, the compounds or elements that react and break down are known as reactants, whereas the compounds or elements that are formed at the end of the reaction are known as products. Chemical reactions can be categorized to predict the products that are formed when different kinds of compounds and molecules come in contact. There are five types of chemical reactions that are mentioned below:

  • Synthesis reactions 
  • Decomposition reactions 
  • Single displacement reactions
  • Double displacement reactions 
  • Combustion reactions 

Synthesis Reactions 
The reactions in which two simple substances combine and form a single compound are called synthesis reactions. Synthesis reactions release energy in the form of heat or light, i.e., they are exothermic reactions.

General formula:

Formation of water
[math]2H₂ + O₂ rarr 2H₂O[/math]

Formation of carbon dioxide
[math]C + O₂ rarr CO₂[/math]

Decomposition Reactions 
The reactions in which one reactant breaks down into one or more products are called decomposition reactions. The decomposition reactions are the opposite of synthesis reactions. Decomposition reactions absorb energy to proceed, i.e., they are endothermic reactions.

General formula:

Decomposition of water
[math]2H₂O rarr 2H₂ + O₂ [/math]

Decomposition of HgO
[math]2HgO rarr 2Hg + O₂ [/math]

Single Displacement Reactions 
The reactions in which a more reactive element displaces a less reactive element from its aqueous salt solution are called single displacement reactions. These reactions are also called substitution reactions. The reactants are always pure elements, such as a pure zinc metal or hydrogen gas, plus an aqueous solution. The general pattern of these reactions is shown below:

A replaced B on the product side to produce AC, and B ends up alone.

[math]Fe + CuSO₄ rarr FeSO₄ + Cu[/math]

[math]Mg + 2HCl rarr MgCl₂ + H₂[/math]

Double Displacement Reactions 
Double displacement reactions are those in which the negative and positive ions get exchanged between the ionic compounds to form a new compound. The general mechanism of the double replacement reactions is:

[math]HCl + NaOH rarr NaCl + H₂O[/math]

Combustion Reactions 
Combustion reactions are reactions in which a substance reacts with oxygen and release some amount of energy in the form of light and heat. The products of the combustion of hydrocarbons are carbon dioxide and water. They are exothermic reactions and as well as can be qualified as combination reactions. The basic form of these reactions is mentioned below:

[math] CXHy + O₂ rarr CO₂ + H₂O[/math]

[math]CH4 + 2O₂ rarr CO₂ + 2H₂O[/math]

[math] C3H8 + 5O₂ rarr 3CO₂ + 4H₂O[/math]

Propane [math](C_3H_8)[/math] is a gaseous hydrocarbon that is commonly used as a fuel source in gas grills.

  • A chemical reaction is a process in which bonds between the reactants are broken to form new bonds between the products. During a chemical reaction, energy is either absorbed or released.
  • Chemical reactions can be categorized into five different types.
  • Synthesis reactions occur when two or more compounds combine to form a new compound, e.g., the formation of water.
  • Decomposition reactions are the opposite of combination reactions. These reactions are those in which one complex compound breaks down into simpler compounds, e.g., photolysis.
  • A single replacement reaction is a reaction in which one element replaces another in a compound. 
  • A double replacement reaction happens when ions get exchanged between two reactants to form a new compound.
  • Combustion reactions are those in which hydrocarbons react with oxygen to form carbon dioxide and water.

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