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

Which of the following reagents would you use to separate $SO_4^{2-}$ ions from a solution containing a mixture of $SO_4^{2-}$ and $Cl^-$ ions?

When a solution of a mixture having two inorganic salts was treated with freshly prepared ferrous sulphate in an acidic medium,a dark brown ring was formed,whereas on treatment with neutral $FeCl_3$,it gave a deep red colour which disappeared on boiling and a brown-red precipitate was formed. The mixture contains:

$X + H_2SO_4 \to Y$ (a colorless gas with a pungent smell).
$Y + K_2Cr_2O_7 + H_2SO_4 \to$ green colored solution.
What are $X$ and $Y$?

Assign $A, B, C, D$ from the given type of reaction.
$BaSO_4 \downarrow + dil. HCl$ $(Excess)$ $\longrightarrow$ No reaction

$A$ reagent consisting of $1$-naphthylamine and sulphanilic acid in acetic acid is used for the detection of: