The reaction ${\mathrm{Cl}}_{2}\left(\mathrm{g}\right)+2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)\to {\mathrm{ClO}}^{-}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)$ represents the process of bleaching. Identify and name the species that bleaches the substances due to its oxidising action.

${\stackrel{0}{\mathrm{Cl}}}_{2}\left(\mathrm{g}\right)+2\stackrel{-2}{\mathrm{O}}\stackrel{+1}{{\mathrm{H}}^{-}}\left(\mathrm{aq}\right)\to \stackrel{+1}{\mathrm{Cl}}\stackrel{-2}{{\mathrm{O}}^{-}}\left(\mathrm{aq}\right)+\stackrel{-1}{{\mathrm{Cl}}^{-}}\left(\mathrm{aq}\right)+{\stackrel{+1}{\mathrm{H}}}_{2}\stackrel{-2}{\mathrm{O}}\left(\mathrm{l}\right)$
In this reaction, O.N. of Cl increases from 0 (in Cl2) to 1 (in ClO-) as well as decreases from 0 (in Cl2) to -1 (in Cl-). So, it acts both reducing as well as oxidisng agent. This is an example of disproportionation reaction. In this reaction, ClO- species bleaches the substances due to its oxidising action. [In hypochlorite ion (ClO-) Cl can decrease its oxidation number from +1 to 0 or -1.]