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: Redox reactions are basically oxidation reduction chemical reactions in which the reactants undergo a change in their oxidation states. Moreover, in case of intramolecular redox reactions, one element of a compound is oxidized while the other is reduced.

Complete step by step answer:
A redox reaction is defined as a chemical reaction in which the electrons are transferred between two reactants participating in the reaction. However, the loss of electrons and the corresponding increase in the oxidation state of a given reactant is called oxidation whereas the gain of electrons and the corresponding decrease in the oxidation state of a reactant is called reduction.
Now, intramolecular redox reactions are those reactions in which one element of a compound is oxidized while the other is reduced. So, from the above listed options the intramolecular reactions are:
 $N{H_4}N{O_2} \to {N_2} + 2{H_2}O$
 $N{H_4}N{O_3} \to {N_2}O + 2{H_2}O$
 $2KCl{O_3} \to 2KCl + 3{O_2}$
But option D i.e. $2{H_2}{O_2} \to 2{H_2}O + {O_2}$ is not an intramolecular redox reaction, instead it is a disproportionation reaction. This is because in this reaction, the same molecule is being oxidized and reduced. Generally, in these types of reactions single reactants are oxidized and reduced.

Hence, option D is correct.

Additional information:
Electron accepting species which tend to undergo a reduction in the redox reactions are known as oxidizing agents whereas an electron donating species which tend to hand over the electrons is referred to as reducing agents. Moreover, these species tend to undergo oxidation.

Note:
Any redox reaction can be broken down into two half-reactions, namely oxidation half reaction and reduction half reaction. But while writing these half reactions separately, one should keep in mind that each of them must be balanced in such a way that all the electrons should be accounted for.