Which of the following reactions are disproportionation reactions? 1 Cu + → Cu 2 + + Cu 2 3 MnO 4 2 - + 4 H + → 2 MnO 4 - + MnO 2 + 2 H 2 O 3 2 KMnO 4 → K 2 MnO 4 + MnO 2 + O 2 4 2 MnO 4 - + 3 Mn 2 +

Question

Which of the following reactions are disproportionation reactions?

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

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

$(3) 2 {KMnO}_{4} \to K_{2} {MnO}_{4} + {MnO}_{2} + O_{2}$

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

Choose the correct answer from the options given below:

TestHub · Accepted Answer

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

$1)$ ${Cu}^{+} ⟶ {Cu}^{2 +} + Cu$

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

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

Oxidation state of $Cu = 0$ .

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

$2)$ $3 {MnO}_{4}^{-} + 4 H^{+} ⟶ 2 {MnO}_{4}^{-} + {MnO}_{2} + 2 H_{2} O$

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

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

Here, reduction is taking place.

$3)$ $2 {KMnO}_{4} ⟶ K_{2} {MnO}_{4} + {MnO}_{2} + O_{2}$

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

$4)$ $2 {MnO}_{4}^{-} + 3 {Mn}^{2 +} + 2 H_{2} O ⟶ 5 {MnO}_{2} + 4 H^{+}$

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

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