## Chemistry: A Molecular Approach (3rd Edition)

The formula of sulfurous acid is $H_{2}SO_{3}$.
Oxyacids with oxanions ending in -ite are named as : $'base name \hspace{1mm}of \hspace{1mm}oxyanion' + ous + acid$ Here, $sulfur$ is the basename and the oxyanion ends in $-ite$. so, the oxyanion is sulfite: $SO_{3}^{2-}$. To balance the charges, 2 hydrogen ions are present. So, the formula of sulfurous acid is $H_{2}SO_{3}$.