S Block Elements Question 104
Question: An unknown inorganic compound (X) loses its water of crystallization on heating and its aqueous solution gives the following reactions :
(a) It gives a white turbidity with dilute $ HCl $ solution
(b) It decolourises a solution of iodine in potassium iodide
(c) It gives a white precipitate with silver nitrate solution which turns black on standing. Identify the compound (X)
Options:
A) $ Na_2CO_3.10H_2O $
B) $ Na_2S_2O_3.5H_2O $
C) $ Na_2SO_4.10H_2O $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ X=Na_2S_2O_3.5H_2O $
$ Na_2S_2O_3+2HCl\xrightarrow{{}} $ $ 2NaCl+H_2O+S+SO_2 $
$ KI_3+2Na_2S_2O_3\xrightarrow{{}} $ $ KI+2NaI+Na_2S_4O_6 $
$ 2AgNO_3+Na_2S_2O_3\xrightarrow{{}} $ $ Ag_2S_2O_3+2NaNO_3 $
$ Ag_2S_2O_3+H_2O\xrightarrow{{}}Ag_2S+H_2SO_4 $
BETA
