Question

Which of the following is not an intramolecular redox reaction?
A.$N{{H}_{4}}N{{O}_{2}}\to {{N}_{2}}+2{{H}_{2}}O$
B.$N{{H}_{4}}N{{O}_{3}}\to {{N}_{2}}O+2{{H}_{2}}O$
C.$2KCl{{O}_{3}}\to 2KCl+3{{O}_{2}}$
D.$2{{H}_{2}}{{O}_{2}}\to 2{{H}_{2}}O+{{O}_{2}}$

Answer 1

Hint: In intramolecular redox reaction, elements of the compound are both reduced and oxidised. For example, $C{{l}_{2}}\to C{{l}^{-}}+Cl{{O}_{3}}^{-}$ is an intramolecular redox reaction.

Complete answer:
In order to answer our question, we need to learn about oxidation and reduction and what is a redox reaction. Now, oxidation can be referred to as adding of oxygen or the removal of hydrogen from a compound. Whereas in case of reduction, either hydrogen is added to the compound or the oxygen is taken away from it. Every compound has an oxidation number to it. If the number is positive, then we say that the compound is oxidised and vice versa, for reduction. Redox reaction is a type of reaction where one compound gets oxidised and another one gets reduced simultaneously, be it in reactant or product side.
In case of intramolecular redox reactions, only a single reactant exists. The products which are formed, have the elements same as that of the reactant, one product is an oxidation product and the other one is reduced. Let us check the options:
\[{{H}_{2}}{{O}_{2}}\to {{H}_{2}}O+{{O}_{2}}\]
Here, the reactant has an oxidation number of -1 and the product has oxidation number -2 and 0 respectively. So, the water is reduced and oxygen is oxidised. But it is a disproportionation reaction.
\[N{{H}_{4}}N{{O}_{2}}\to {{N}_{2}}+2{{H}_{2}}O\]
In this reaction, the reactant has oxidation number -3, and the product has oxidation number +3 and 0. So, it is an intramolecular redox reaction.
\[N{{H}_{4}}N{{O}_{3}}\to {{N}_{2}}O+2{{H}_{2}}O\]
Here, reactant has oxidation number -3 and product has oxidation number +5 and +1, hence it is an intramolecular redox reaction.
\[2KCl{{O}_{3}}\to 2KCl+3{{O}_{2}}\]
Here, reactant has oxidation number +5 and product has oxidation number -1 and 0, hence it is an intramolecular redox reaction.

So, option A , being a disproportionation reaction, is the answer for this question.

Note:
The intramolecular redox reactions can be carried out by various methods, which include heating, adding reagents as well as using catalysts.