1.

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

Answer»

`Na_(2)SO_(3),SO_(2),Cr_(2)(SO_(4))_(3)`
`Na_(2)S_(2)O_(3),SO_(2),Cr_(2)(SO_(4))_(3)`
`Na_(2)S,SO_(2),Cr_(2)(SO_(4))_(3)`
`Na_(2)SO_(4),SO_(2),Cr_(2)(SO_(4))_(3)`

Solution :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`


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