Which of the following reactions are disproportionation reaction? a 2 C u + → C u 2 + + C u 0 b 3 M n O 4 2 - + 4 H + → 2 M n O 4 - + M n O 2 + 2 H 2 O c 2 K M n O 4 → ∆ K 2 M n O 4 + M n O 2 + O 2 d

Question

Which of the following reactions are disproportionation reaction?

$(a)$ $2 C u^{+} \to C u^{2 +} + C u^{0}$

$(b)$ $3 M n O_{4}^{2 -} + 4 H^{+} \to 2 M n O_{4}^{-} + M n O_{2} + 2 H_{2} O$

$(c)$ $2 K M n O_{4} \overset{∆}{\to} K_{2} M n O_{4} + M n O_{2} + O_{2}$

$(d)$ $2 M n O_{4}^{-} + 3 M n^{2 +} + 2 H_{2} O \to 5 M n O_{2} + 4 H^{\oplus}$

Select the correct option from the following:

NEET 2019 (All India)

TestHub · Accepted Answer

The redox reactions in which the same species is getting oxidised (increase in oxidation number) and reduced (decrease in oxidation number).

(i) $\overset{(+ 1)}{2 C u^{+}} \to \overset{(+ 2)}{C u^{+ 2}} + \overset{(0)}{C u^{0}} \to$ Disproportionation

(ii) $\overset{(+ 6)}{3 M n O_{4}^{2 -}} + 4 H^{+} \to \overset{(+ 7)}{2 M n O_{4}^{-}} + \overset{(+ 4)}{M n O_{2}} + 2 H_{2} O \to$ Disproportionation

(iii) $\overset{(+ 7)}{2 K M n O_{4}} \overset{Δ}{\to} \overset{(+ 6)}{K_{2} M n O_{4}} + \overset{(+ 4)}{M n O_{2}} + O_{2}$

Only reduction is happening here.

(iv) $\overset{(+ 7)}{2 M n O_{4}^{-}} + \overset{(+ 2)}{3 M n^{+ 2}} \to \overset{(+ 4)}{5 M n O_{2}}$

Different species are getting oxidised and reduced. Hence, the correct options are (i) and (ii) only.

Chemistry - Redox Reactions Question with Solution | TestHub

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