Sodium carbonate is prepared by Solvay process. Which of the...

Here $CaC{l}_{2}$ is formed as a by-product
$N{H}_{3} + {H}_{2}O + C{O}_{2} \to N{H}_{4}HC{O}_{3}$ …(i)
$N{a}^{+} + C{l}^{-} + N{H}_{4}^{+} + HC{O}_{3}^{-} \to \mathop{NaHC{O}_{3}}_{( ppt . )} + N{H}_{4}^{+} + C{l}^{-}$ …(ii)
For step (i), $C{O}_{2}$ is produced by heating limestone.
$CaC{O}_{3} \to CaO + C{O}_{2}$
CaO so-obtained is slaked with ${H}_{2}O$ and $N{H}_{4}Cl$ produced in step (ii) reacts to form $CaC{l}_{2}$ as a by-product.
$\text{CaO}\text{+}{\text{H}}_{\text{2}} \text{O} \to {\text{Ca(OH)}}_{\text{2}} \overset{{\text{NH}}_{\text{4}} \text{Cl}}{\to} {\text{CaCl}}_{\text{2}} \text{+}{\text{2NH}}_{\text{3}} \text{+}{\text{2H}}_{\text{2}} \text{O}$