Which of the following represents disproportionation reaction-

(a) 2Cu⁺ ---> Cu²⁺ +Cu

(B)3I₂ ---> 5I^-  + I⁺⁵

(d) 2HCHO --^OH--> HCOO^- + CH₃OH
(c)H₂o + Cl_​2 + ClO-  + 2H​+

Dear Student,

Disproportionation reactions are a special type of redox reactions. In a disproportionation reaction an element in one oxidation state is simultaneously oxidised and reduced. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least three oxidation states. The element in the form of reacting substance is in the intermediate oxidation state; and both higher and lower oxidation states of that element are formed in the reaction.
disproportionation reaction : a, b and d

2 Cu+ (aq) → Cu2+(aq) + Cu(s)

3I₂ ---> 5I^-  + I⁺⁵

2HCHO + OH^------------>HCOO^-+CH₃OH

Regards