Discussion Forum

 A compound X  on heating gives a colourless gas. The residue is dissolved in water to obtain Y. Excess CO₂ is passed through aqueous solution of Y when Z  is formed. Z on gentle heating gives back X  . The compound X is 

Answer:

Explanation:

$CaCO_{3}$  $\underrightarrow{\triangle}$ $CaO+CO_{2}\uparrow$

   X                                   colourless gas

 $CaO+H_{2}O\rightarrow Ca(OH)_{2}$

  Residue                        Y

$Ca(OH)_{2}+2CO_{2}\rightarrow  Ca(HCO_{3})_{2}$

   Y             excess                      Z

$Ca(HCO_{3})_{2}$  $\underrightarrow{\triangle}$   $CaCO_{3}+CO_{2}\uparrow+H_{2}O$

    Z                                      X