types of reaction

What are Types of Chemical Reactions in Chemistry?

I have taught chemistry for a decade now and one of the things I discovered that is so paramount in chemistry is the reactions and bonding patterns of atoms.

This is so crucial and is equally applied in materials science as we go higher in chemistry, but we only concentrate on the types of chemical reactions.

There are several types of reactions in Chemistry that you should have come across even without taking note of the exact type of chemical reaction. These reactions are used often in Chemistry for different processes.

I will teach you the different types of chemical reactions in Chemistry so you be able to write and predict products in chemical reactions.

There are actually five basic types of chemical reactions in Chemistry we will be discussing briefly.

The 5 types of Reactions in Chemistry

1. Combustion Reactions

A combustion reaction is the type of reaction in which a substance burns in oxygen to release heat and sometimes light.

The model reaction is just a combination of the elements

     2Mg + O2 –> 2MgO

A combustion reaction sometimes could be complete or incomplete.

For example, the combustion of carbon

    C + O2  –> CO2

This reaction is a complete combustion reaction.

Take a look at this one

    2C + O2    à 2CO

What makes a combustion reaction complete or incomplete?

It actually depends on the availability of air (oxygen), in a limited supply of air reaction likely to be incomplete while in excess air complete reaction

Other examples of combustion reactions are the combustion of metals and hydrocarbons. The combustion reaction is one of the common types of reactions in Chemistry that usually appear in different O-level exams.

 CH4 + 2O2   –> CO2 + 2H2O

  C2H6   +  7/2   O2  –> 2CO2 + 3H2O

Additionally, it is very pertinent to remember that Combustion reactions are always exothermic.

A reaction is said to be exothermic when it releases heat into the environment

A reaction is said to be endothermic when it absorbs heat from the environment.

2. Combination Reaction or Synthesis Reaction

A combination reaction is a chemical reaction in which two or more substances react to combine into a single compound.

The general model of combination reactions is   A + B  –> AB

The clear distinction of combination reactions is that a single product is always formed.

in writing combination reactions, Please remember that Oxygen, hydrogen halogen is diatomic and should be written as so.  

                 Na + ½ Cl2 –> NaCl

                 K + ½ Br2  –> KBr

Diatomic elements imply that they are molecules and can retain Chemical properties when they stand alone.

3. Decomposition Reactions

A decomposition reaction is a reaction in which a substance breaks down into two or simpler substances.

Decomposition reactions are sometimes hastened by heat.

A decomposition reaction is more like the reverse of combination reactions and takes this model

            AB  –> A +B


CaCO3 –>   CaO + CO2

MgCO3 –> MgO + CO2

Please remember that Carbonates of group one elements do not decompose

Also, nitrates do decompose differently

2NaNO3  –>   2NaNO2 + O2

2Ca(NO3)2 –> 2CaO + 4NO2 + O2

Decomposition reactions are hastened sometimes by heating or simply put increasing temperatures.

Recall that the rate of a reaction is usually increased by adding catalyst, increasing temperature, concentration, etc.

Usually, when talking about types of chemical reactions in Chemistry, students only focus on Decomposition reactions. There are other types of reactions as we discuss them in this guide.

4. Displacement Reactions or Single Displacement Reaction

A displacement reaction otherwise called a single replacement reaction is the type of reaction in which an element displaces another similar element in a reaction to form a compound.

Usually, in displacement reaction, a more electropositive element will displace a less electropositive element from its salt.

Similarly, a more electronegative element will displace a less electronegative element from its salt.

By similar as mentioned, we mean of the same nature, the reactivity series will be handy in mastering the displacement reactions.

The model of displacement reaction is as follows

A + BC –> AC + B


Mg + ZnCl2  –> MgCl2 + Zn

Cl2 + NaBr   –> NaCl  + Br2

If you are struggling with balancing chemical equations, then you need to check my full post on how to balance chemical equations

5. Double Decomposition reactions or Double replacement reaction/Doub;e Displacement Reactions

A double displacement reaction is a reaction between two soluble salts to form an insoluble product(precipitate) and a soluble product. This reaction is usually called the precipitation reaction because an insoluble product is formed.

In double decomposition, there is an exchange of ions between the compound to form new products.

The reaction model is given below

AB + CD   –> AD + CB

e.g      KCl + AgNO3   –>  KNO3 + AgCl   

          The precipitate is silver I chloride (AgCl)

          Ba(NO3)2 +Na2SO4  –> BaSO4 +NaNO3

The precipitate is Barium sulphate ( BaSO4 )

          2NaCl  + Pb(NO3)2 –>    PbCl2 + 2NaNO3

The precipitate is Lead II chloride ( PbCl2 )

Please I want you to understand that you can write any equation on Double decomposition reaction by just knowing the insoluble salts. All you need to do is check the two soluble salts that can yield the insoluble salts.

I know you may be wondering, how do know the product that will be a precipitate. it is actually simple, I know the solubility rule of salts.

Please you can check my post on how to name compounds this will really help you to name every chemical compound you come across.

You only need to know the solubility of salts and then you can literally determine if a particular salt will be soluble in water or not. I have done a good post on how to determine the solubility of salts and factors affecting the solubility of salts.

Types of reactions Chemistry is a very important concept in Chemistry that needs students to practice some of the various examples of equations in these reactions.

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