Question

Which of the following is not an intramolecular redox reaction?

• A. $2KCl{O}_3\to 2KCl+3O_2$
• B. $2M{n}_2{O}_7\to 4Mn{O}_2+3O_2$
• C. $2H_2{O}_2\to 2H_{2}O+O_2$
• D. None of the above

Answer 1

The correct option is C $2H_2{O}_2\to 2H_{2}O+O_2$

In a Intramolecular redox reaction, oxidation of one atom and reduction of the other atom occurs within the same molecule.
a)
$\stackrel{+1}{K}\stackrel{+5}{Cl}\stackrel{-2}{O_3}\to \stackrel{+1}{K}\stackrel{-1}{Cl}+3\stackrel{0}{O_2}$
As in this case oxidation and reduction takes place through a single molecule. i.e. in $KCl{O}_3$ ,
$\stackrel{+5}{Cl}\to \stackrel{-1}{Cl}$--Reduction.
$\stackrel{-2}{O_3}\to \stackrel{0}{O_2}$-- Oxidation.

b)
$\stackrel{+7}{2M{n}_2}\stackrel{-2}{O_7}\to \stackrel{+4}{4Mn}\stackrel{-2}{O_2}+3\stackrel{0}{O_2}$
As in this case oxidation and reduction takes place through a single molecule. i.e. in $M{n}_2{O}_7$ ,
$\stackrel{+7}{M{n}_2}\to \stackrel{+4}{Mn}$--Reduction.
$\stackrel{-2}{O_7}\to \stackrel{0}{O_2}$-- Oxidation

c)
$\stackrel{+1}{H_2}\stackrel{-1}{O_2}\to \stackrel{+1}{H_2}\stackrel{-2}{O}+3\stackrel{0}{O_2}$
$\stackrel{-1}{O_2}\to \stackrel{-2}{O}$--Reduction.
$\stackrel{-1}{O_2}\to \stackrel{0}{O_2}$-- Oxidation
It is a disproportionation reaction and not intramolecular redox reaction as $O_2$ from its is simultaneously reduced and oxidised to form two different products.