The brown ring test is used for the detection of which radical?

$X$ (salt) + $AgNO_3$ $(aq.) \to \underset{(\text{Yellow ppt.})}{Y \downarrow}$ (soluble in excess of $NH_3$ solution). Salt $X$ does not contain:

Select the $CORRECT$ statement based on the following reactions:
$\text{Salt } 'X' (\text{soluble}) + \text{dil. } H_2SO_4 \to \text{gas } (B) + \text{neutral oxide } (C) + 'Y'$
$\text{Salt } 'X' (\text{soluble}) \xrightarrow{BaCl_2 \text{ solution}} \text{White ppt. } 'Z'$
$\text{aq. sol. of gas } (B) \xrightarrow{H_2S(g)} 'Y' + \text{neutral oxide } (C)$
Given these reactions,identify the correct statement regarding salt $'X'$.

For the identification of which ion is $Na_2CO_3$ $NOT$ useful?

Sodium nitroprusside,when added to an alkaline solution of sulphide ions,produces a purple colour due to the formation of:

$S^{2-}$ and $SO_3^{2-}$ can be distinguished by using