Question

Which selection is an example of a decomposition reaction?
(a)- $2K+{{F}_{2}}\to 2KF$
(b)- $2Al+6HCl\to 2AlC{{l}_{3}}+3{{H}_{2}}$
(c)- ${{C}_{3}}{{H}_{8}}+5{{O}_{2}}\to 3C{{O}_{2}}+4{{H}_{2}}O$
(d)- $2NaHC{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}$

Answer 1

Hint: Decomposition reaction is also known as chemical decomposition or chemical breakdown. In this reaction, two or more products are made from only one reactant.

Complete step by step answer:
A decomposition reaction is also known as chemical decomposition or chemical breakdown is a process in which a single component is simplified into two or more components.
A decomposition reaction is the exact reverse of the chemical synthesis because in chemical synthesis the two or more reactant combines to form product whereas in decomposition reaction one reactant is split into fragments.
We can differentiate other reactions from decomposition reaction by the number of reactants because in decomposition reaction only one reactant is present.
Some energy is used in the decomposition reaction because the bonds break apart to produce simpler molecules or compounds. From this, we can say that most of the decomposition reactions are endothermic which requires energy, although exceptions exist.
So, let us see all the options one by one:

(a)- $2K+{{F}_{2}}\to 2KF$
In this reaction, two reactants combine to form one product. Hence, this reaction is not a decomposition reaction.
This option is incorrect.

(b)- $2Al+6HCl\to 2AlC{{l}_{3}}+3{{H}_{2}}$
In this reaction, two reactants combine to form two products. Hence, this reaction is not a decomposition reaction.
This option is also incorrect.

(c)- ${{C}_{3}}{{H}_{8}}+5{{O}_{2}}\to 3C{{O}_{2}}+4{{H}_{2}}O$
In this reaction, two reactants combine to form two products. Hence, this reaction is not a decomposition reaction.
This option is also incorrect.

(d)- $2NaHC{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}$
In this reaction, one reactant is decomposed to form 3 products. Hence, it is a decomposition reaction.
This option is correct. So, the correct answer is “Option D”.

Note: The decomposition reaction is sometimes considered as an undesired chemical reaction because some conditions like humidity, heat, radiation, etc reactants readily decompose to products.