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    

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 :

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.