Question

Which of the following reactions are disproportionation reaction?
a)\(2Cu^{+}\rightarrow Cu^{2+}+Cu^{0}\)
\(b)3MnO_4^{2-}+4H^{+} \rightarrow2MnO_4^{-}+MnO_2+2H_2O\)
\(c)2KMnO_4\frac{\Delta}{\rightarrow}K_2MnO_4+MnO_2+O_2\)
\(d)2MnO_4^{-}+3Mn^{2+}+2H_2O \rightarrow 5MnO_2+4H^\oplus\)
Select the correct option from the following:

• A. (a) and (b) only
• B. (a), (b) and (c)
• C. (a), (c) and (d)
• D. (a) and (d) only

Answer 1

The Correct Option is A

To determine which of the given reactions are disproportionation reactions, we first need to understand the concept of a disproportionation reaction. A disproportionation reaction is a specific type of redox reaction in which a single substance is simultaneously oxidized and reduced, forming two different products.

Now, let's analyze each given reaction:

1. Reaction (a): \(2Cu^{+} \rightarrow Cu^{2+} + Cu^{0}\)
   • The copper ion \(Cu^+\) is both oxidized and reduced in this reaction.
   • Oxidation: \(Cu^+ \rightarrow Cu^{2+} + e^-\)
   • Reduction: \(Cu^+ + e^- \rightarrow Cu^0\)
   • Result: This is a disproportionation reaction.
2. Reaction (b): \(3MnO_4^{2-} + 4H^+ \rightarrow 2MnO_4^- + MnO_2 + 2H_2O\)
   • Manganese in \(MnO_4^{2-}\) is both oxidized and reduced.
   • Oxidation: \(MnO_4^{2-} \rightarrow MnO_4^-\)
   • Reduction: \(MnO_4^{2-} \rightarrow MnO_2\)
   • Result: This is a disproportionation reaction.
3. Reaction (c): \(2KMnO_4 \frac{\Delta}{\rightarrow} K_2MnO_4 + MnO_2 + O_2\)
   • This reaction does not feature manganese being both oxidized and reduced.
   • Result: This is not a disproportionation reaction.
4. Reaction (d): \(2MnO_4^- + 3Mn^{2+} + 2H_2O \rightarrow 5MnO_2 + 4H^+\)
   • Manganese is not simultaneously oxidized and reduced in this reaction.
   • Result: This is not a disproportionation reaction.

From the analysis above, reactions (a) and (b) show characteristics of disproportionation reactions where the same element undergoes both oxidation and reduction. Therefore, the correct option is:

(a) and (b) only