A chemical $A$ is used for the preparation of washing soda to recover ammonia. When $\mathrm{CO}_2$ is…
A chemical $A$ is used for the preparation of washing soda to recover ammonia. When $\mathrm{CO}_2$ is bubbled through an aqueous solution of $A$, the solution tums milky. It is used in white washing due to disinfectant nature. What is the chemical formula of $A$ ?
$\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$
$\mathrm{CaO}$
$\mathrm{Ca}(\mathrm{OH})_2$
$\mathrm{CaCO}_3$
Solution
$\mathrm{Ca}(\mathrm{OH})_2$ is used in the preparation of washing soda $\left(\mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O}\right.$ ) to recover ammonia $\left(\mathrm{NH}_3\right)$.
$
\begin{aligned}
& 2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow 2 \mathrm{NH}_3+\mathrm{CaCl}_2+\mathrm{H}_2 \mathrm{O} \\
& \mathrm{Ca}(\mathrm{OH})_2+\mathrm{CO}_2 \longrightarrow \mathrm{CaCO}_3 \downarrow+\mathrm{H}_2 \mathrm{O}
\end{aligned}
$
A milkiness $\mathrm{Ca}(\mathrm{OH})_2$ is used in white washing due to its disinfectant nature.
Hence, the correct option is (3)