From the given reactions identify the disproportionation reaction...

The reaction in which one reactant gets oxidized, and the same reactant gets reduced is known as disproportionation reaction.&

$\overset{0}{Cl}2 ( g ) + 2K\overset{- 1}{I} ( aq ) ⟶ 2K\overset{0}{C}l ( aq ) + \overset{- 1}{I}2 ( s )$

In the above reaction different elements undergoing oxidation and reduction. Hence, It is not a~disproportionation reaction.~

$\overset{0}{Cl}2 ( g ) + 2{OH}^{-} ( aq ) ⟶ \overset{+ 1}{Cl}O^{-} ( aq ) + {Cl}^{-} ( aq ) + {H}_{2}O ( l )$

In the above reaction chlorine is undergoing oxidation as well as reduction.~Hence, It is a disproportionation reaction.~

$\overset{0}{Mg} ( s ) + 2\overset{+ 1}{H}Cl ( aq ) ⟶ \overset{+ 2}{Mg}{Cl}_{2} ( aq ) + \overset{0}{H}2 ( g )$

In the above reaction magnesium is undergoing oxidation and hydrogen ion undergoing reduction.~Hence, It is not a~disproportionation reaction.~

$2{H}_{2}\overset{- 1}{O}2 ( aq ) ⟶ 2{H}_{2}\overset{- 2}{O} ( l ) + \overset{0}{O}2 ( g )$

In the above reaction peroxide is undergoing oxidation as well as reduction.& Hence, It is a disproportionation reaction.&