Question

A metal carbonate X on reacting with acid and gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at the anode during electrolysis of brine is passed on dry Y, and it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G, and Z.

Answer 1

Calcium:

• Calcium is a metal having an atomic number $20$ and atomic symbol $\mathrm{Ca}$.

Reaction of Calcium carbonate with acid:

• When Calcium carbonate $\left({\mathrm{CaCO}}_3\right)$ reacts with Hydrochloric acid $\left(\mathrm{HCl}\right)$, it produces Calcium chloride $\left({\mathrm{CaCl}}_2\right)$ along with the liberation of carbon dioxide$\left({\mathrm{CO}}_2\right)$ and water$\left({\mathrm{H}}_2\mathrm{O}\right)$.
• The chemical reaction can be depicted as:

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Reaction of ${\mathrm{CO}}_2$ with slaked lime:

• When carbon dioxide gas is passed through Slaked lime or Calcium hydroxide $\left({\mathrm{CaOH}}_2\right)$, it gives calcium carbonate $\left({\mathrm{CaCO}}_3\right)$.
• The chemical reaction can be depicted as:

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Electrolysis of brine solution:

• Brine solution is a solution of sodium chloride $\left(\mathrm{NaCl}\right)$ and water $\left({\mathrm{H}}_2\mathrm{O}\right)$.
• The gas that is obtained at the anode during electrolysis of brine is passed on dry slaked lime is Chlorine gas.
• The reaction taking place at the anode is depicted as:
• $2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\to {\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-}$

Reaction of chlorine gas with dry lime water:

• Lime water is Calcium hydroxide $\left({\mathrm{CaOH}}_2\right)$.
• When chlorine gas is passed on dry lime water, it gives bleaching powder which is used for disinfecting water.
• When dry chlorine gas is passed over the dry slaked lime, calcium oxychloride$\left({\mathrm{CaOCl}}_2\right)$ is formed.
• The chemical reaction can be depicted as:

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)\to {\mathrm{CaOCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, X is calcium carbonate $\left({\mathrm{CaCO}}_3\right)$, Y is slaked lime $\left({\mathrm{CaOH}}_2\right)$, Z is bleaching powder $\left({\mathrm{CaOCl}}_2\right)$, and G is chlorine gas $\left({\mathrm{Cl}}_2\right)$.