Question

Among the following observations, the correct one that differentiates between $SO^{2-}_{3}$ and $SO^{2-}_{4}$ is

• A. Both form precipitate with $BaCl_2, SO_3^{2-}$ dissolves in $HCl$ but $SO_4^{2-}$ does not
• B. $SO_3^{2-}$ forms precipitate with $BaCl_2, SO_4^{2-}$ does not
• C. $SO_4^{2-}$ forms precipitate with $BaCl_2, SO_3^{2-}$ does not
• D. Both form precipitate with $BaCl_2, SO_4^{2-}$ dissolves in $HCl$ but $SO_3^{2-}$ does not

Answer 1

Answer: (A)

$SO _{3}^{2-}$ and $SO _{4}^{2-}$ when treated with $BaCl _{2}$, give white ppt of $BaSO _{3}$ and $BaSO _{4}$ respectively.
$BaCl _{2}+ SO _{3}^{2-} \longrightarrow \underset{\overset{\text{Barium}}{\text{sulphide}}}{BaSO _{3}}+2 Cl ^{-}$
$BaCl _{2}+ SO _{4}^{2-} \longrightarrow \underset{\text{Barium sulphate}}{BaSO _{4}+2 Cl ^{-}}$
Barium sulphate Out of these two, $SO _{3}^{2-}$ is soluble in $HCl$ but $SO _{4}^{2-}$ does not.