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JEE Main levelSingle correct optionDifficulty 2 of 3qa173

A sodium salt on treatment with dilute $HCl$ gives a pale yellow turbidity and a gas with a pungent smell of burning sulphur on warming. The anion is

A $S X^{2 -}$
B $S X_{2} O X_{3} X^{2 -}$
C $CO X_{3} X^{2 -}$
D $SO X_{3} X^{2 -}$

Answer: B

Thiosulphate disproportionates in acid:

S X_{2} O X_{3} X^{2 -} + 2 H X^{+} SO X_{2} + S + H X_{2} O

. The colloidal sulphur gives the turbidity and

SO X_{2}

gives the pungent smell. Sulphite gives

SO X_{2}

without turbidity, sulphide gives

H X_{2} S

and carbonate gives odourless

CO X_{2}

.

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