A substance on treatment with dilute `H_(2)SO_(4)` liberates a colourless gas which produces `(I)` turbidity with baryta water and `(ii)` turns acidified dichromate solution green. The reaction indicates the presence of `:`

Options

A. `NO_(2^(-))`
B. `S^(2-)`
C. `SO_(3)^(2-)`
D. `CO_(3)^(2-)`

Answer

C

Explanation

Both carbonate and sulphide react with dil. `H_2SO_4` to form `CO_2 and SO_2` respectively. Both `CO_2 and SO_2` form turbidity with baryta water. But `CO_2` cannot turn acidified `K_2Cr_2O_7` solution green. Only `SO_2` can turn acidified `K_2Cr_2O_7` solution green.
`{:(,K_(2)Cr_(2)O_(7)+4H_(2)SO_(4) to K_(2)SO_(4)+Cr_(2)(SO_(4))_(3)+4H_(2)O+3O),(,3SO_(2)+3H_(2)O+3O to 3H_(2)SO_(4)),(,overline(K_(2)Cr_(2)O_(7)+H_(2)SO_(4)+3SO_(2) to K_(2)SO_(4)+Cr_(2)(SO_(4))_(3)+H_(2)O)):}`