An aqueous solution of a gas `(X)` gives the following reactions :
(a) It decolourises an acidified `K_2 Cr_2 O_7` solution.
(b) On boiling with `H_2 O_2`, cooling it and then adding an aqueous solution of `BaCl_2`, a precipitate insoluble in `conc. HCl` is obtained.
(c) On passing `H_2 S` in the solution, white turbidity is obtained.
Identify `(X)` and give equations for steps `(a), (b)` and `(c)`.

Answer

`X=SO_(2)`

Explanation

(i) `Cr_(2)O_(7)^(2-)+3SO_(2)+2H^(+)to2Cr^(3+)+3SO_(4)^(2-)+H_(2)O`
(ii) `H_(2)O_(2)toH_(2)O+O`
`SO_(2)+H_(2)O+[O]toH_(2)SO_(4)`
`H_(2)SO_(4)+Ba^(2+)toBaSO_(4)darr("white")+2H^(+)`
(iii) `H_(2)S+SO_(2)overset(H_(2)O)to2H_(2)O+2Sdarr("white turbidity")`