TYPES OF CHEMICAL REACTIONS

Ø In a chemical reaction, the atoms of the reacting molecules or elements are rearranged to form new molecules.

Ø Old chemical bonds between atoms are broken and new chemical bonds are formed.

Ø Bond breaking absorbs energy whereas bond formation releases energy.

Example :

Ø Methane + Oxygen → Carbon dioxide + Water

TYPES OF CHEMICAL REACTIONS -

Combination reactions:

Ø A combination reaction is a reaction in which two or more reactants combine to form a compound.

Ø It is otherwise called 'synthesis reaction' or 'composition reaction'.

Ø When a reactant ‘A’ combines with ‘B’, it forms the product ‘AB’.

Ø The generalised scheme of a combination reaction is given below:

Decomposition reactions:

Ø In a decomposition reaction, a single compound splits into two or more simpler substances under suitable conditions.

Ø It is the opposite of the combination reaction.

Ø The generalised scheme of a decomposition reaction is given below:

Single Displacement Reactions:

Ø It is a reaction between an element and a compound.

Ø When they react, one of the elements of the compound-reactant is replaced by the element-reactant to form a new compound and an element.

Ø The general schematic representation of a single displacement reaction is given as:

Double Displacement Reactions:

Ø When two compounds react, if their ions are interchanged, then the reaction is called double displacement reaction.

Ø The ion of one compound is replaced by the ion of the another compound.

Ø Ions of identical charges are only interchanged, i.e., a cation can be replaced by other cations.

Ø This reaction is also called ‘Metathesis Reaction’.

Ø The schematic representation of a double displacement reaction is given below:

Combustion Reactions:

Ø A combustion reaction is one in which the reactant rapidly combines with oxygen to form one or more oxides and energy (heat).

Ø So in combustion reactions, one of the reactants must be oxygen.

Ø Combustion reactions are majorly used as heat energy sources in many of our day to day activities.

Ø For instance, we use LPG gas for domestic cooking purposes.

Ø We get heat and flame from LPG gas by its combustion reaction of its constituent gases.

Differences between reversible and irreversible reactions: