Question

Gas $A$ is bubbled through slaked lime when a white precipitate is formed. On prolonged bubbling, the precipitate is dissolved. On heating the resultant solution, the white precipitate reappears with the evolution of gas $B$. The gases $A$ and $B$ respectively are:

• A. $ CO_{2} $ and $CO$
• B. $CO$ and $ CO_{2}$
• C. $CO$ and $CO$
• D. $CO_2$ and $ CO_{2} $

Answer 1

Answer: (D)

According to the question
$Ca ( OH )_{2}+ \underset{(A)}{ CO _{2}} \ce{->[{\Delta}]} \underset{\text{white ppt}}{CaCO _{3}}+ H _{2} O$
$CaCO _{3}+ H _{2} O + CO _{2} \rightarrow \underset{\text{soluble}}{Ca \left( HCO _{3}\right)_{2}}$
$Ca \left( HCO _{3}\right)_{2} \ce{->[{\Delta}]} CaO + H _{2} O +\underset{(B)}{2 CO _{2}}$
$\therefore [ A ]$ and $[ B ]$ both are $CO _{2} . g$