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Byju's Answer

Standard XII

Chemistry

Chemical Reactivity (Group 1)

The aqueous s...

Question

The aqueous solution of an unknown sodium salt gives the following reactions.
I. It decolorises a solution of iodine in potassium iodide.
II. It gives white turbidity with $d i l . H C l$ solution.
III. It gives a white precipitate with $A g N O_{3}$ solution which changes colours and finally becomes black no standing.
The unknown sodium salt is :

sodium thiosulphate

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sodium bisulphite

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sodium sulphite

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sodium sulphide

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Solution

The correct option is A sodium thiosulphate
The unknown sodium salt is sodium thiosulphate. $N a_{2} S_{2} O_{3}$
I. It decolorises a solution of iodine in potassium iodide.
$2 N a_{2} S_{2} O_{3} + I_{2} \to N a_{2} S_{4} O_{6} + 2 N a I$
II. It gives white turbidity with dil. $H C l$ solution.
$N a_{2} S_{2} O_{3} + 2 H C l \to 2 N a C l + H_{2} O + S O_{2} + S$
III. It gives a white precipitate with $A g N O_{3}$ solution which changes colours and finally becomes black no standing.
$N a_{2} S_{2} O_{3} + 2 A g N O_{3} \to A g_{2} S_{2} O_{3} + 2 N a N O_{3}$
$A g_{2} S_{2} O_{3} + H_{2} O \to A g_{2} S ↓ + H_{2} S O_{4}$

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Similar questions

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(III) It gives a white precipitate with

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