Preparation of Baking Soda (Sodium Hydrogen Carbonate, $NaHCO_3$):
Baking soda is commonly produced on a large scale by the Solvay process, which involves reacting a cold and concentrated solution of sodium chloride (brine) with ammonia and carbon dioxide.
Chemical Equation:
$NaCl(aq) + H_2O(l) + CO_2(g) + NH_3(g) \rightarrow NH_4Cl(aq) + NaHCO_3(s)$
Sodium hydrogen carbonate is sparingly soluble in water and thus precipitates out.

Important Uses:
1. In baking: It is a component of baking powder (a mixture of baking soda and a mild edible acid like tartaric acid). When heated or mixed with water, it produces carbon dioxide, which causes bread or cake to rise.
$2NaHCO_3(s) \xrightarrow{\text{Heat}} Na_2CO_3(s) + H_2O(l) + CO_2(g)$
2. As an antacid: Due to its alkaline nature, it neutralizes excess acid in the stomach, providing relief from indigestion.
3. In soda-acid fire extinguishers: It produces carbon dioxide gas, which helps in extinguishing fires.
4. As a mild antiseptic.