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Introduction to Reduction Reaction

A chemicalreaction involves the conversion of a chemical substance into anotherby cleavage of certain chemical bond and formation of new one.Substances take parts in chemical reaction are called as reactant andnewly formed substances are known as product. Chemical reactions canbe classified in various types on the basis of type of reactants andproducts or the way followed by reaction. Some common types ofchemical reactions are as follow;


  1. Combinationreaction

  2. Decompositionreaction

  3. Displacementreaction

  4. Redoxreaction

  5. Neutralisationreaction


Redoxreactions involve change in oxidation number of reacting substance.This reaction is a combination of two opposite reactions called asoxidation and reduction reaction. Both reactions are complimentary toeach other as one reaction happens with one reactant; another must beinvolved in same reaction. Let’s discuss about reduction reaction;


DefineReduction Reaction: It definition states that a reaction in which theoxidation number of reacting substance reduce is called asreduction-reaction. In other words, in a reaction like these a reactant accept electrons and convert in low oxidation state. Overall gainof electrons or hydrogen or loss of oxygen or decrease in oxidationstate is known as reduction reaction. Such reactions which showreduction of chemical substances are known asReduction Chemical Reaction.


Reduction-reactionare generally held with oxidation reactions which are just oppositeto reduction, therefore theloss of electrons or hydrogen or gain of oxygen or increase inoxidation state is knownas oxidation reaction. A reaction which involves both reactions;oxidation and reduction is known as Redox reaction. For example; theformation of hydrofluoric acid from hydrogen and fluorine is anexample of Redox reaction.

H2 +F2 -> 2 HF

Oxidation:H2 -> 2 H+ +2 e 

Reduction:F2 +2 e -> 2 F 


We canobserve reduction reaction example in laboratory during experiments.Let’s have a look on some examples of reduction reactions;

  • Reductionof silver ions in their aqueous solution:2 Ag+ (aq)+ 2 e- 2 Ag (s)

  • Reductionof oxygen to oxide ion:


  • Reductionof carbon dioxide to carbon monoxide:

  • Reductionof copper(II) ions: Cu2+ +2 e− -> Cu

  • Reductionof hydrogen peroxide to hydroxyl ions: H2O2 +2 e -> 2 OH

  • Inthe presence of an acid reductionof nitrate to nitrogen :

2 NO3 +10 e +12 H+ -> N2 +6 H2O

  • Reductionof nitrogen to ammonia:

N2+ 3H2 -> 2NH3

  • Reductionof unsaturated hydrocarbon to saturated hydrocarbons:

CH2=CH2+ H2 -> CH3-CH3