Which of the following compounds is used in the Solvay process for the manufacture of sodium carbonate: ${\text{NH}}_3$, $\text{NaOH}$, ${\text{Na}}_2{\text{SO}}_4$, or $\text{KCl}$?

Solution

1. The Solvay process uses brine ($\text{NaCl}$), limestone (${\text{CaCO}}_3$), and ammonia (${\text{NH}}_3$).
2. The reaction involves $\text{NaCl}+{\text{NH}}_3+{\text{CO}}_2+{\text{H}}_2\text{O}\to {\text{NaHCO}}_3+{\text{NH}}_4\text{Cl}$.
3. Ammonia is recovered and recycled in the process.
4. Hence the answer is (A).