An unknown salt X reacts with hot conc. H2SO4 to produce a brown coloured gas which intensies on addition on copper turnings. On adding dilute ferrous sulphate solution to an aqueous solution of X and then carefully adding conc. H2SO4 along the sides of the test tube, a brown complex Y is formed at the interface between the solution and H2SO4. Identify X and Y
and write the chemical equation involved in the reaction.
