Answer
$H_{2}SO_{3}$
Work Step by Step
Sulfite anion ($SO_{3}^{2-}$) has a -2 charge. In order to form an acid, hydrogen ions are needed. Hydrogen ion has a +1 charge. In order to balance it, 2 atoms of hydrogen ions are needed. Thus, the formula will be $H_{2}SO_{3}$. When naming, -ite in sulfite is changed to -ous and acid is added at the end. Therefore, the name will be sulfurous acid.
