Q. A white precipitate is formed when gas $A$ bubbled through slaked lime solution and the precipitate dissolves on prolonged bubbling of gas $A$ . White precipitate reappears on heating the solution with evolution of gas $B$ . Find the gases $A$ and $B$ .

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A

$CO$ and $CO$

B

$CO_{2}$ and $CO$

C

$CO$ and $CO_{2}$

D

$CO_{2}$ and $CO_{2}$

Solution:

$Ca\left(\right.OH\left(\left.\right)_{2 \left(\right. aq \left.\right)}+\left(CO\right)_{2 \left(\right. g \left.\right)} \rightarrow \left(CaCO\right)_{3 \left(\right. s \left.\right)}\left(\right.A\left.\right)+H_{2}O$
$\left(CaCO\right)_{3 \left(\right. s \left.\right)}+H_{2}O+\left(CO\right)_{2 \left(\right. g \left.\right)} \rightarrow Ca\left(\left(HCO\right)_{3}\right)_{2}\right)_{\left(\right. aq \left.\right)}$
$Ca\left(\left(HCO\right)_{3}\right)_{2}\overset{\Delta }{ \rightarrow }\left(CaCO\right)_{3 \left(\right. g \left.\right)}+H_{2}O+\left(CO\right)_{2 \left(\right. g \left.\right)}$
.

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