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

Which statement is not true with respect to the nitrate ion test?

When chlorine water is added to an aqueous solution of potassium halide in the presence of chloroform,a violet colour is obtained. On adding more chlorine water,the violet colour disappears,and a colourless solution is obtained. This test confirms the presence of which of the following in the aqueous solution?

$A$ salt solution is treated with chloroform drops. Then it is shaken with chlorine water. The chloroform layer becomes violet. The solution contains:

When $BaCl_2$ is added to a clear solution of compound $(X)$,a heavy white precipitate is formed,which is insoluble in dilute $HCl$. What is compound $(X)$?

$A$ sodium salt gives a white precipitate with $MgCl_2$ only upon heating. What is the anion of the sodium salt?