A white crtystalline salt A reacts with dilute HCl to liberate a suffocating gas B and also forms a yellow precipitate. The gas B turns potassium dichromate acidified with dilute `H_(2)SO_(4)` to a green coloured solution C.A,B and C are respectively

Options

A. `Na_(2)SO_(3),SO_(2),Cr_(2)(SO_(4))_(3)`
B. `Na_(2)S_(2)O_(3),SO_(2),Cr_(2)(SO_(4))_(3)`
C. `Na_(2)S,SO_(2),Cr_(2)(SO_(4))_(3)`
D. `Na_(2)SO_(4),SO_(2),Cr_(2)(SO_(4))_(3)`

Answer

B

Explanation

Dil. HCl decomposes `Na_(2)S_(2)O_(3)(A)` with evolution of gas which possesses a suffocating smell of burning sulphur i.e., `SO_(2)(B)` and yellow ppt. of sulphur is obtained.
`underset((A))(Na_(2)S_(2)O_(3))+2HCl to2NaCl+underset((B))(SO_(2))uarr+underset("(Yellow ppt.)")(Sdarr+H_(2)O)`
When acidified potassium dichromate paper is exposed to the gas, it attains a green colour due to the formation of chromium sulphate.
`K_(2)Cr_(2)O_(7)+H_(2)SO_(4)+3SO_(2)toK_(2)SO_(4)+Cr_(2)underset("(C) green")(Cr_(2)(SO_(4))_(3))+H_(2)O`