An aqueous solution of a gas (X) gives the following reactions:
(i) It decolourises an acidified K2Cr2O7 solution.
(ii) On boiling with H2O2 and cooling it and then adding an aqueous solution of BaCl2, a ppt. insoluble in dilute HCl, is produced.
(iii) On passing H2S in the solution, white turbidity is formed.
Identify (X).