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

Which reagent is used to remove $SO_4^{2-}$ and $Cl^{-}$ ions from a solution?

Given below are two statements:
Statement $I$: Griess-Ilosvay test is used for the detection of nitrite ion,which involves the use of sulphanilic acid and $\alpha$-naphthylamine reagent.
Statement $II$: In the above test,sulphanilic acid is diazotized by the acidified nitrite ion,which on further coupling with $\alpha$-naphthylamine forms an azo-dye.
In the light of the above statements,choose the correct answer from the options given below.

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

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

Anion which can react with $dil. H_2SO_4$ is