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A white crystalline salt [A] reacts with...

A white crystalline 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 ad C are respectively.

A

`Na_(2)SO_(3),SO_(2),Cr(SO_(4))_(3)`

B

`Na_(2)S_(2)O_(3),SO_(2),Cr(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)`

Text Solution

Verified by Experts

The correct Answer is:
B
Dil. HCl decomposes `Na_(2)S_(2)O_(3)` (A) with evolution of a gas which possesses a suffocating smell of burning sulphur i.e., `SO_(2)(B)` and yellow ppt. of sulphur is obtained .
`Na_(2)underset("(A)")(S_(2))O_(3) + 2HCl to 2NaCl + underset("(B)")(SO_(2)) uarr + underset("(yellow ppt)")(S darr) + 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) to K_(2)SO_(4) + Cr_(2)underset("Green")underset("(C)")((SO_(4)))_(3) + H_(2)O`
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