Which of the following reactions are disproportionation reactions?

(i) Cu+    Cu2+ + Cu

(ii) 3MnO4- + 4H+         2MNO4- + MnO2 + 2H2O

(iii) 2KMnO4          K2MnO4 + MnO2 + O2

(iv) 2MnO4- + 3Mn2+ + 2H2O         5MnO2 + 4H+

1.  (i)

2.  (i) , (ii) and (iii)

3.  (ii) , (iii) and (iv)

4.  (i) and (iv)

NEETprep Answer: 
 
The reaction in which oxidation as well as reduction, occur upon same atom simultaneously is known as disproportionation reaction.