S Block Elements Question 252
Question: A solid compound ‘X’ on heating gives $ CO_2 $ gas and a residue. The residue mixed with water forms ‘Y’. On passing an excess of $ CO_2 $ through ‘Y’ in water, a clear solution, ‘Z’ is obtained. On boiling ‘Z’, compound ‘X’ is reformed. The compound ‘X’ is
[CBSE PMT 2004]
Options:
A) $ Na_2CO_3 $
B) $ K_2CO_3 $
C) $ Ca{{(HCO_3)}_2} $
D) $ CaCO_3 $
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Answer:
Correct Answer: D
Solution:
The given compound x must be $ CaCO_3 $ . It can be explained by following reactions, $ \underset{\text{(x)}}{\mathop{CaCO_3}}\xrightarrow{\Delta }\underset{Residue}{\mathop{CaO}}+CO_2\uparrow $ ; $ CaO+H_2O\to \underset{\text{(y)}}{\mathop{Ca{{(OH)}_2}}} $
$ Ca{{(OH)}_2}+CO_2+H_2O\to \underset{z}{\mathop{Ca(HCO_3)}} $
$ Ca{{(HCO_3)}_2}\xrightarrow{\Delta }\underset{\text{(x)}}{\mathop{CaCO_3}}+CO_2\uparrow +H_2O $
BETA
