Answer
Please see the work below.
Work Step by Step
We know that sulphites are converted into sulphates by reaction with hydrogen peroxide.
$SO_3^{-2}+H_2O_2\rightarrow SO_4^{-2}+H_2O$
Sulphate ions are treated with barium chloride to produce barium sulphate precipitate. The reaction is given as follows:
$SO_4^{-2}+BaCl_2\rightarrow BaSO_4+2Cl^-$
