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Types of Redox Reactions | Chemistry Class 11 - NEET PDF Download

There are four main types of redox reactions:

  1. Combination Reactions
  2. Decomposition Reactions 
  3. Displacement Reactions
  4. Disproportionation Reactions

Combination Reactions 

  • Combination Reactions involve the combination of two compounds to form a single compound.
  • A combination reaction may be denoted in the manner: A + B → C 
  • Either A and B or both A and B must be in the elemental form for such a reaction to be a redox reaction. 
  • All combustion reactions, that make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen, are redox reactions.

Examples of Combustion ReactionsExamples of Combustion Reactions

Question for Types of Redox Reactions
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Which of the following reactions involves the combination of two compounds to form a single compound?
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Decomposition Reactions

  • Decomposition reactions are the opposite of combination reactions. 
  • Precisely, a decomposition reaction leads to the breakdown of a compound into two or more components, at least one of which must be in the elemental state. 

Examples of Decomposition ReactionsExamples of Decomposition Reactions

  • It may carefully be noted that there is no change in the oxidation number of hydrogen in methane under combination reactions and that of potassium in potassium chlorate. This may also be noted here that all decomposition reactions are not redox reactions. For example, the decomposition of calcium carbonate is not a redox reaction.

Types of Redox Reactions | Chemistry Class 11 - NEET

Displacement Reactions 

  • In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. 
  • It may be denoted as: X + YZ → XZ + Y 
  • Displacement reactions fit into two categories: metal displacement and non-metal displacement. 

(a) Metal Displacement: 

  • A metal in a compound can be displaced by another metal in the uncombined state. 
  • Metal displacement reactions find many applications in metallurgical processes, where pure metals are obtained from their compounds in ores. 
  • A few such examples are:

Some Examples of Metal Displacement ReactionsSome Examples of Metal Displacement ReactionsIn each case, the reducing metal is a better-reducing agent than the one that is being reduced, demonstrating a greater capability to lose electrons compared to the one that is reduced.

(b) Non-metal Displacement: 

  • The non-metal displacement redox reactions include hydrogen displacement and a rarely occurring reaction involving oxygen displacement. 
  • All alkali metals and some alkaline earth metals (Ca, Sr, and Ba), which are very good reductants, will displace hydrogen from cold water.

Types of Redox Reactions | Chemistry Class 11 - NEET

  • Less active metals such as magnesium and iron react with steam to produce dihydrogen gas.

Types of Redox Reactions | Chemistry Class 11 - NEET

  • Many metals, including those which do not react with cold water, are capable of displacing hydrogen from acids. Dihydrogen from acids may even be produced by metals that do not react with steam, with cadmium and tin being examples of such metals. A few examples for the displacement of hydrogen from acids are:

Types of Redox Reactions | Chemistry Class 11 - NEET

  • Very less active metals, which may occur in the native state such as silver (Ag) and gold (Au), do not react even with hydrochloric acid. 

Question for Types of Redox Reactions
Try yourself:
Which type of reaction involves the breakdown of a compound into two or more components, at least one of which must be in the elemental state?
View Solution

Disproportionation Reactions 

Disproportionation reactions are a special type of redox reaction. In such reactions, an element in one oxidation state is simultaneously oxidized and reduced. 

Key points about disproportionation reactions include:

  • An element in one oxidation state undergoes both oxidation and reduction in a disproportionation reaction.
  • At least one of the reacting substances always contains an element that can exist in at least three oxidation states.
  • The element in the form of the reacting substance is in the intermediate oxidation state.
  • Both higher and lower oxidation states of that element are formed in the reaction.

Example: The decomposition of hydrogen peroxide is a familiar example of a disproportionation reaction, where oxygen undergoes disproportionation:

Types of Redox Reactions | Chemistry Class 11 - NEET

Here, the oxygen of peroxide, initially present in the –1 state, is converted to zero oxidation state in O2 and decreases to –2 oxidation state in H2O.

The document Types of Redox Reactions | Chemistry Class 11 - NEET is a part of the NEET Course Chemistry Class 11.
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Types of Redox Reactions
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FAQs on Types of Redox Reactions - Chemistry Class 11 - NEET

1. What is a combination reaction?
Ans. A combination reaction is a type of chemical reaction where two or more reactants combine to form a single product. This reaction is also known as a synthesis reaction. An example of a combination reaction is the reaction between hydrogen gas and oxygen gas to form water: 2H2 + O2 → 2H2O.
2. What is a decomposition reaction?
Ans. A decomposition reaction is a type of chemical reaction where a compound breaks down into two or more simpler substances. This reaction is the opposite of a combination reaction. An example of a decomposition reaction is the breakdown of hydrogen peroxide into water and oxygen gas: 2H2O2 → 2H2O + O2.
3. What is a displacement reaction?
Ans. A displacement reaction is a type of chemical reaction where an element in a compound is replaced by another element. This reaction occurs when a more reactive element displaces a less reactive element from its compound. An example of a displacement reaction is the reaction between zinc and hydrochloric acid, where zinc displaces hydrogen from the acid: Zn + 2HCl → ZnCl2 + H2.
4. What is a disproportionation reaction?
Ans. A disproportionation reaction is a type of chemical reaction where a single substance is simultaneously oxidized and reduced, resulting in the formation of two different products. This reaction occurs when an element in a compound simultaneously undergoes both oxidation and reduction. An example of a disproportionation reaction is the decomposition of hydrogen peroxide into water and oxygen gas: 2H2O2 → 2H2O + O2.
5. What are the types of redox reactions?
Ans. The types of redox reactions include combination reactions, decomposition reactions, displacement reactions, and disproportionation reactions. In combination reactions, two or more reactants combine to form a single product. In decomposition reactions, a compound breaks down into simpler substances. In displacement reactions, an element displaces another element in a compound. In disproportionation reactions, a single substance is simultaneously oxidized and reduced, resulting in the formation of two different products. Redox reactions involve the transfer of electrons between species, where one species is oxidized (loses electrons) and another is reduced (gains electrons).
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