Question

A compound X on heating produce a colorless gas Y and metal oxide Z. The metal oxide is yellow when hot and show white color when it is cooled. Identify X, Y and Z?

• A. $\mathrm{X}={\mathrm{ZnCO}}_3,\mathrm{Y}={\mathrm{CO}}_2,\mathrm{Z}=\mathrm{ZnO}$
• B. $\mathrm{X}={\mathrm{CaCO}}_3,\mathrm{Y}={\mathrm{CO}}_2,\mathrm{Z}=\mathrm{CaO}$
• C. $\mathrm{X}={\mathrm{AgNO}}_3,\mathrm{Y}={\mathrm{NO}}_2,\mathrm{Z}=\mathrm{AgO}$
• D. $\mathrm{X}={\mathrm{CuSO}}_4,\mathrm{Y}={\mathrm{SO}}_2,\mathrm{Z}=\mathrm{CuO}$

Answer 1

The correct option is B

$\mathrm{X}={\mathrm{CaCO}}_3,\mathrm{Y}={\mathrm{CO}}_2,\mathrm{Z}=\mathrm{CaO}$

Explanation for the correct answer

(B) Option, B is the correct answer.

Calcium carbonate ($CaC{O}_3$) which is compound X on heating produces Carbon dioxide gas ($C{O}_2$) which is colorless in nature represented by Y and form metal oxide represented by $\mathrm{CaO}$ i.e. calcium oxide which is yellow in color when it is hot it and becomes white in color when it is cooled.

$\mathrm{X}={\mathrm{CaCO}}_3,\mathrm{Y}={\mathrm{CO}}_2,\mathrm{Z}=\mathrm{CaO}$

Reaction can be shown as:

$\underset{\mathrm{Calcium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}\stackrel{∆}{\to }\underset{\mathrm{Calcium}\mathrm{oxide}}{\mathrm{CaO}\left(\mathrm{s}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}$

Therefore the correct option is (B).