UPSC Combined Geo-Scientist, Mains · 2016 · Mains Paper I

Q1(d). Disproportionation and its reverse

Question

Consider the following reaction: 3ClO⁻ → 2Cl⁻ + ClO₃⁻. Name the type of such reactions and give name and example of the reverse type.

The reaction is disproportionation; its reverse type is comproportionation (synproportionation).

Chlorine in ClO⁻ has oxidation number +1. It is reduced to -1 in Cl⁻ and oxidised to +5 in ClO₃⁻.
Two chlorine atoms each gain two electrons and one loses four, so the electron balance is satisfied.
In comproportionation, two oxidation states of an element form one intermediate oxidation state. For example, Ag + Ag²⁺ → 2Ag⁺: 0 and +2 give +1.

The full model answer

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CoversDisproportionationits reverseRedox chemistry