Question

Aqueous solution of a salt $(A)$ forms a dense white precipitate with $BaCl_2$ solution. The precipitate dissolves in dilute $HCl$ to produce a gas $(B)$ which decolourises acidified $KMnO_4$ solution $A$ and $B$ respectively are :

• A. $BaSO_3, SO_2$
• B. $BaSO_4, H_2S$
• C. $BaSO_3, H_2S$
• D. $BaSO_4, SO_2$

Answer 1

Answer: (A)

$BaSO_3, SO_2$

Answer 2

The corresponding reactions are

$BaCl _{2}+ Na _{2} SO _{3} \rightarrow BaSO _{3}+2 NaCl$
$BaSO _{3}+2 HCl \rightarrow BaCl _{2}+ SO _{2}+ H _{2} O$

Salt $A$ is $Na _{2} SO _{3}$ and the dense white precipitate is $BaSO _{3}$ (Barium sulfite).

Gas $B$ is $SO _{2}$. It decolourises acidified $KMnO _{4}$ solution because of its reducing nature.

The corresponding reaction is:

$2 KMnO _{4}+5 SO _{2}+2 H _{2} O \rightarrow K _{2} SO _{4}+2 MnSO _{4}+2 H _{2} SO _{4}$