Answer
$HClO_{2}$( aq ) is chlorous acid.
Work Step by Step
Oxyacids with oxanions ending in -ite are named as : $ 'base name \hspace{1mm}of \hspace{1mm}oxyanion' + ous + acid$
The base name of oxyanion $ClO_{2}^{-}$ (chlorite) is $chlor$ , so $HClO_{2}$( aq ) is chlorous acid.