Question

Discuss the various reactions that occur in the Solvay process.

Answer 1

Solvay process is used to prepare sodium carbonate.

When carbon dioxide gas is bubbled through a brine solution saturated with ammonia, sodium hydrogen carbonate is formed. This sodium hydrogen carbonate is then converted to sodium carbonate.

Step 1: Brine solution is saturated with ammonia.

This ammoniated brine is filtered to remove any impurity.

Step 2: Carbon dioxide is reacted with this ammoniated brine to result in the formation of insoluble sodium hydrogen carbonate.

$$\begin{gathered} {\mathrm{NH}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2\to {\mathrm{NH}}_4{\mathrm{HCO}}_3 \\ \mathrm{NaCl}+{\mathrm{NH}}_4{\mathrm{HCO}}_3\to {\mathrm{NaHCO}}_3+{\mathrm{NH}}_4\mathrm{Cl} \end{gathered}$$

Step 3: The solution containing crystals of NaHCO₃ is filtered to obtain NaHCO₃.

Step 4: NaHCO₃ is heated strongly to convert it into NaHCO₃.

Step 5: To recover ammonia, the filtrate (after removing NaHCO₃) is mixed with Ca(OH)₂ and heated.

$\mathrm{Ca}(\mathrm{OH}{)}_2+2{\mathrm{NH}}_4\mathrm{Cl}\to 2{\mathrm{NH}}_3+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{CaCl}}_2$

The overall reaction taking place in Solvay process is