Which of the following ions produces violet vapors upon reaction with concentrated $H_2SO_4$?

$A$ salt gives violet vapours when treated with conc. $H_2SO_4$. It contains

Choose the correct matching $:-$

Column-$I$	Column-$II$
$P$. $NaBr + \text{Conc. } H_2SO_4 \rightarrow$	$A$. Colourless gas
$Q$. $Na_2S + \text{dil. } HCl \rightarrow$	$B$. Brown colour
$R$. $NaNO_2 + \text{dil. } HCl \rightarrow$	$C$. Rotten egg smell
$S$. $NaNO_3 + \text{Conc. } H_2SO_4 \rightarrow$	$D$. Paramagnetic

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

Formation of $Na_4[Fe(CN)_5NOS]$,a purple coloured complex formed by addition of sodium nitroprusside in sodium carbonate extract of salt indicates the presence of $:$

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