JEE Main 2024 — Redox Reactions Question with Solution

The compounds or ions or elements in which central atom has intermediate oxidation state undergo a disproportionation reaction.

Disproportionation reactions are the reactions in which the same element/compound gets oxidised and reduced simultaneously.

1)${\mathrm{Cu}}^{+} \to {\mathrm{Cu}}^{2+} + \mathrm{Cu}$

2) $2{\mathrm{H}}_2{\stackrel{-1}{\mathrm{O}}}_2\stackrel{}{\to }{\mathrm{H}}_2\stackrel{-2}{\mathrm{O}}+{\stackrel{0}{\mathrm{O}}}_2$

$3) 3 {\mathrm{Cl}}_2 + 6 {\mathrm{OH}}^{-} \to 5{\mathrm{Cl}}^{-} + {{\mathrm{ClO}}_3}^{-}+ 3 {\mathrm{H}}_2\mathrm{O}$

$4) 2{\mathrm{NO}}_2(\mathrm{g})+2{\mathrm{OH}}^{-}(\mathrm{aq})\to {{\mathrm{NO}}_2}^{-}(\mathrm{aq})+{\mathrm{H}}_2\mathrm{O}(\mathrm{l})+{{\mathrm{NO}}_3}^{-}$

$5) {\mathrm{P}}_4+3{\mathrm{OH}}^{-}+3{\mathrm{H}}_2\mathrm{O}\to {\mathrm{PH}}_3+3{\mathrm{H}}_2{{\mathrm{PO}}_2}^{-}$

Here, the chlorine reactant is in oxidation state $0$, and if we look at the products, the chlorine in the Cl⁻ ion has an oxidation number of $-1$, where it has undergone reduction. Meanwhile, the oxidation number of the chlorine in the ${{{\mathrm{ClO}}_3}^{-}}_{}$ ion is $+5$, which means it has been oxidised.

Hence, ${\mathrm{H}}_2{\mathrm{O}}_2, {\mathrm{Cu}}^{+}, {\mathrm{Cl}}_2,{\mathrm{ClO}}_3,{\mathrm{P}}_4,{\mathrm{NO}}_2$ shows disproportionation reaction.