Question

Which of the following reactions are disproportionation reaction?
(a) 2Cu⁺ → Cu²⁺ + Cu⁰
(b) 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O
(c) 2KMnO₄ --∆→K₂MnO₄ + MnO₂ + O₂
(d) 2MnO₄⁻ + 3Mn²⁺ + 2H₂0 → 5Mn0₂ + 4H⊕
Select the correct option from the following :
(1) (a) and (b) only
(2) (a), (b) and (c)
(3) (a), (c) and (d)
(4) (a) and (d) only

Answer 1

"a" and "b" are disproportionation reactions.

Step by step explanation:

Disproportionation reaction

In this reaction,  a molecule is dissociated into two products, one of higher oxidation state and another of lower oxidation state than compare to  the reactant molecule.

Disproportionation reaction is a typical reduction reaction.

From the given reactions,

(a)

      $\bold{2Cu^{+}\rightarrow Cu^{2+}+Cu}$

In this reaction, reactant copper has +1 charge, where as product copper has +2(higher) and another copper has zero (less).

(b)

          $\bold{3MnO_{4}^{2-}+4H^{+}\rightarrow 2MnO_{4}^{-}+MnO_{2}+2H_{2}O}$

$MnO_{4}^{2-}$ has -6 oxidation state in product side. And product side it has -1 and  +4.

Therefore, "a" and "b" are disproportionation reactions.

Hence, correct option is 1.