Which ion's salt solution produces a violet layer when chlorine water and chloroform are added?

The incorrect statement in respect of the chromyl chloride test is:

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

In the qualitative analysis of nitrate,a brown ring is formed due to the formation of:

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:

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