Question

`[X]+H_(2)SO_(4) to [Y]` a colourless gas with irritating smell, `[Y]+K_(2)Cr_(2)O_(7)+H_(2)SO_(4) to` green solution.
`[X]` and `[Y]` are respectively :
A. `SO_(3)^(2-),SO_(2)`
B. `Cl^(-),HCl`
C. `S^(2-),H_(2)S`
D. `CO_(3)^(2-),CO_(2)`

Answer 1

Correct Answer - A
`SO_(2)` is colourless irritating gas which reduces acidified `K_(2)Cr_(2)O_(7)` to green coloured `Cr_(2)(SO_(4))_(3).CO_(2)` is colourless and odour less , `H_(2)S` has rotten egg smell and reduces acidified `K_(2)Cr_(2)O_(7)` to green coloured `Cr_(2)(SO_(4))_(3)` with a yellow precipitate of sulphur.
`SO_(3)^(2-)+2H^(+)toSO_(2)+H_(2)O , Cr_(2)O_(7)^(2-) + 3SO_(2)+2H^(+) to 2Cr^(3+) ("green solution") +3SO_(4)^(2-)+H_(2)O`