When $\mathrm{Cl}_2$ gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of…

When $\mathrm{Cl}_2$ gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from
  1. zero to +1 and zero to -5
  2. zero to -1 and zero to +5
  3. zero to -1 and zero to +3
  4. zero to +1 and zero to -3

Solution

When chlorine gas reacts with hot and concentrated $\mathrm{NaOH}$ solution, it disproportionates into chloride $\left(\mathrm{Cl}^{-}\right)$and chlorate $\left(\mathrm{ClO}_3^{-}\right)$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.

Asked in: NEET 2012 (Screening)

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