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 $:$

$A$ salt,which on heating with conc. $H_2SO_4$ gives violet vapours,is

Which one of the following anions is not easily removed from aqueous solutions by precipitation?

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

In a test tube containing a salt,a few drops of dilute $\text{H}_2\text{SO}_4$ were added,which gave colourless vapours having the smell of vinegar. The vapours turned the blue litmus paper red. Identify the correct anion from the following:

The brown ring test is used to detect the presence of which ion?