Question

A metal carbonate X on reacting with an acid 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 anode during electrolysis of brine is passed on dry Y, It gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.

Answer 1

The gas G obtained at anode during the electrolysis of brine is chlorine. The compound Z used for disinfecting drinking water is bleaching powder. It is formed on reacting chlorine with dry slaked lime i.e., Ca(OH)₂. It is denoted as Y This means that the metal carbonate X is calcium carbonate. Upon heating, it evolves CO₂ gas which gives back X on reacting with calcium hydroxide. The chemical reactions involved are listed :

`underset((X))("CaCO"_3) + underset("(Acid)")(2"HCl") -> "CaCl"_2 + "H"_2"O" + "CO"_2`

`underset("(Y)")("Ca"("OH")_2) + "CO"_2 -> underset ((x))("CaCO"_3) + "H"_2"O"`

`"Ca"("OH")_2 + underset("(From brine)")underset("(G)") -> underset("Bleaching Powder")underset("(Z)")("CaOCl"_2) + "H"_2"O"`