Discuss the various reactions that occur in the Solvay process.

(N/A) The Solvay process is used for the industrial preparation of sodium carbonate $(Na_{2}CO_{3})$. The process relies on the low solubility of sodium hydrogen carbonate $(NaHCO_{3})$,which precipitates when sodium chloride $(NaCl)$ reacts with ammonium hydrogen carbonate $(NH_{4}HCO_{3})$.
$1$. Ammonia is dissolved in a concentrated solution of sodium chloride,and $CO_{2}$ is passed through it to form ammonium carbonate,which then converts to ammonium hydrogen carbonate:
$2NH_{3} + H_{2}O + CO_{2} \rightarrow (NH_{4})_{2}CO_{3}$
$(NH_{4})_{2}CO_{3} + H_{2}O + CO_{2} \rightarrow 2NH_{4}HCO_{3}$
$2$. The $NH_{4}HCO_{3}$ reacts with $NaCl$ to precipitate $NaHCO_{3}$:
$NH_{4}HCO_{3} + NaCl \rightarrow NH_{4}Cl + NaHCO_{3}$
$3$. The $NaHCO_{3}$ crystals are filtered and heated to produce sodium carbonate:
$2NaHCO_{3} \rightarrow Na_{2}CO_{3} + CO_{2} + H_{2}O$
$4$. Ammonia is recovered by treating the $NH_{4}Cl$ solution with calcium hydroxide $(Ca(OH)_{2})$,producing calcium chloride $(CaCl_{2})$ as a by-product:
$2NH_{4}Cl + Ca(OH)_{2} \rightarrow 2NH_{3} + CaCl_{2} + 2H_{2}O$