JEE Main 2024 — Chemistry Physical Chemistry

2024mcqeasy

Which of the following reactions are disproportionation reactions?

$(1){\mathrm{Cu}}^{+}\rightarrow {\mathrm{Cu}}^{2+}+\mathrm{Cu}$

$(2) 3{\mathrm{MnO}}_{4}^{2-}+4{H}^{+}\rightarrow 2{\mathrm{MnO}}_{4}^{-}+{\mathrm{MnO}}_{2}+2{H}_{2}O$

$(3)2{\mathrm{KMnO}}_{4}\rightarrow {K}_{2}{\mathrm{MnO}}_{4}+{\mathrm{MnO}}_{2}+{O}_{2}$

$(4)2{\mathrm{MnO}}_{4}^{-}+3{\mathrm{Mn}}^{2+}+2{H}_{2}O\rightarrow 5{\mathrm{MnO}}_{2}+4{H}^{+}$

Choose the correct answer from the options given below:

Official previous-year question

Held on 1 Feb 2024 · Verified 6 Jul 2026.

Options

A
$(1),(2)$
B
$(2),(3),(4)$
C
$(1),(2),(4)$
D
$(1),(4)$

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Solution

In disproportionation reaction, both oxidation and reduction of same chemical species occurs.

Oxidation is gain in oxidation number.

Reduction is loss in oxidation number.

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

Oxidation state of ${\mathrm{Cu}}^{+}=+1$ .

Oxidation state of ${\mathrm{Cu}}^{2+}=+2$ .

Oxidation state of $\mathrm{Cu}=0$ .

Here, ${\mathrm{Cu}}^{+}$ is getting both reduced and oxidised.

$2)$ $3{\mathrm{MnO}}_{4}^{-}+4{H}^{+}\longrightarrow 2{\mathrm{MnO}}_{4}^{-}+{\mathrm{MnO}}_{2}+2{H}_{2}O$

Oxidation state of $\mathrm{Mn}$ in ${{\mathrm{MnO}}_{4}}^{-}=+7$ .

Oxidation state of $\mathrm{Mn}$ in ${\mathrm{MnO}}_{2}=+4$ .

Here, reduction is taking place.

$3)$ $2{\mathrm{KMnO}}_{4}\longrightarrow {K}_{2}{\mathrm{MnO}}_{4}+{\mathrm{MnO}}_{2}+{O}_{2}$

Here in the reaction, $\mathrm{Mn}$ is changing its oxidation state from $+7$ to $+6$ and $+4$ . In both cases, reduction is occurring.

$4)$ $2{\mathrm{MnO}}_{4}^{-}+3{\mathrm{Mn}}^{2+}+2{H}_{2}O\longrightarrow 5{\mathrm{MnO}}_{2}+4{H}^{+}$

Here in the reaction, product with $\mathrm{Mn}$ in only one, so there is no possibility of both oxidation and reduction reactions at the same time.

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Solution

In disproportionation reaction, both oxidation and reduction of same chemical species occurs.

Oxidation is gain in oxidation number.

Reduction is loss in oxidation number.

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

Oxidation state of ${\mathrm{Cu}}^{+}=+1$ .

Oxidation state of ${\mathrm{Cu}}^{2+}=+2$ .

Oxidation state of $\mathrm{Cu}=0$ .

Here, ${\mathrm{Cu}}^{+}$ is getting both reduced and oxidised.

$2)$ $3{\mathrm{MnO}}_{4}^{-}+4{H}^{+}\longrightarrow 2{\mathrm{MnO}}_{4}^{-}+{\mathrm{MnO}}_{2}+2{H}_{2}O$

Oxidation state of $\mathrm{Mn}$ in ${{\mathrm{MnO}}_{4}}^{-}=+7$ .

Oxidation state of $\mathrm{Mn}$ in ${\mathrm{MnO}}_{2}=+4$ .

Here, reduction is taking place.

$3)$ $2{\mathrm{KMnO}}_{4}\longrightarrow {K}_{2}{\mathrm{MnO}}_{4}+{\mathrm{MnO}}_{2}+{O}_{2}$

Here in the reaction, $\mathrm{Mn}$ is changing its oxidation state from $+7$ to $+6$ and $+4$ . In both cases, reduction is occurring.

$4)$ $2{\mathrm{MnO}}_{4}^{-}+3{\mathrm{Mn}}^{2+}+2{H}_{2}O\longrightarrow 5{\mathrm{MnO}}_{2}+4{H}^{+}$

Here in the reaction, product with $\mathrm{Mn}$ in only one, so there is no possibility of both oxidation and reduction reactions at the same time.

JEE Main 2024 — Chemistry Physical Chemistry

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JEE Main 2024 — Chemistry Physical Chemistry

Options

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Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry