question_answer

When \[\text{C}{{\text{l}}_{\text{2}}}\] gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from     [AIPMT (S) 2012]

A)       zero to +1 and zero to -5

B) zero to -1 and zero to +5

C) zero to -1 and zero to +3

D) zero to +1 and zero to -3

Correct Answer: B

Solution :

[b] When chlorine gas reacts with hot and concentrated    NaOH    solution,    it disproportionate into chloride \[(C{{l}^{-}})\] and chlorate \[(ClO_{3}^{-})\] ions.

In this process, oxidation number of chlorine changes from 0 to -1 and 0 to +5.

Note In disproportionation reactions, the same element undergoes oxidation as well as reduction.