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Please note that the types of chemical reactions are not the same thing as the types of chemical combinations. In Inorganic Chemistry, there are various types of Chemical reactions with each type having its own distinguishing features. Some of the types include:

  • Combination or Addition Reaction
  • Decomposition Reaction
  • Displacement or Replacement Reaction
  • Double Decomposition Reaction
  • Thermal Decomposition Reaction
  • Catalyzed Reaction
  • Reversible Reaction
  • Thermal Dissociation
  • Oxidation-Reduction(Redox) Reaction

Combination/Addition Reaction

Combination or Addition reaction occurs when two or more elements or compounds combine to form a new single compound.

A + B C

Example: A mixture of gaseous hydrogen and Chlorine, in the presence of sunlight, explodes to give hydrogen Chloride gas

H2(g) + Cl2(g) 2HCl(g)

Decomposition Reaction

This reaction occurs when a solid compound is heated and splits into two or more substances. One of the products is a gas, while the other is a liquid or solid called residue. It is the opposite of the combination/addition reaction outlined above.

C A + B

An example of a decomposition reaction is when red powdered mercury(II) oxide is heated, it produces liquid mercury and oxygen gas.

2HgO(s) 2Hg(I) + O2(g)

Displacement Or Replacement Reaction

A displacement reaction occurs when an element A displaces another element B from a compound of B.

A + BC AC + B

This type of reaction when a metal higher up the activity series(A) displaces a metal lower in the activity series. The activity series is a totally different topic which we would write about in another article.

Double Decomposition Reaction

A double Decomposition reaction occurs when two compounds react to produce two new compounds by exchange of ions.


Common types of double decomposition reactions include Precipitation reactions, neutralization reactions, and the formation of volatile acids.

Reversible Reaction

This is a chemical or physical process that can be made to proceed either forward or backward under different conditions of temperature and pressure.

A + B C + D

also, the reaction can also be possible like this C + D A + B

Thermal Dissociation

This is a type of reversible reaction in which only a change in temperature determines the direction of the reaction.

Catalyzed Reaction

A catalyzed reaction is one that employs the use of a catalyst to speed up the rate of the reaction. A catalyst is a substance that alters the rate of a reaction without being used up itself. There are two types of catalysts namely artificial and natural.


The term Redox is coined from two words reduction and oxidation. The two processes occur simultaneously in the same reaction.

Laws Of Chemical Combination

There are various laws that govern Chemical Combinations and some of the common laws include:

Law Of Conservation Of Mass(Or Matter)

This law states that during the course of a chemical reaction, the matter is neither created nor destroyed.

Law Of Definite Proportions Or Constant Compositions

This law was suggested by Proust(1799) and it states that all pure substances of the same compound contain the same elements combined in the same proportion by mass or all pure samples of the same compound have the same percentage composition by mass.

Law Of Multiple Proportion

The law states that when two elements A and B combine to form two or more compounds, the various masses of A, which combine with a fixed mass of the other elements B, are in the ratio of small whole numbers.

All these laws can be verified but we would do that in another article. If you have any questions, please drop them in the comment section below.

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