Question

The reaction \[\ce{Cl2 (g) + 2OH- (aq) -> ClO- (aq) + Cl- (aq) + H2O (l)}\] represents the process of bleaching. Identify and name the species that bleaches the substances due to its oxidising action.

Answer 1

 \[\ce{\overset{0}{Cl2} (g) + 2\overset{-2}{O}\overset{+1}{H-} (aq) -> \overset{+1}{Cl}\overset{-2}{O-} (aq) + \overset{-1}{Cl-} (aq) + \overset{+1}{H2} \overset{-2(oxidation number)}{O(l)}}\]

In this reaction, O.N. of \[\ce{Cl}\] increases from 0 (in \[\ce{Cl2}\]) to +1 (in \[\ce{CIO-}\]) and decreases to -1 (in \[\ce{Cl-}\]). Therefore, \[\ce{Cl2}\] is both oxidized to \[\ce{CIO-}\] and reduced to Cl^–. Since \[\ce{Cl-}\] ion cannot act as an oxidizing agent (because it cannot decrease its O.N. lower than -1), therefore, \[\ce{Cl2}\] bleaches substances due to oxidizing action of hypochlorite, \[\ce{ClO}\] ion.