1. Sodium Hydroxide (NaOH) — Caustic Soda

Castner-Kellner Cell (Mercury Process):

• Electrolyte: Brine (NaCl solution)
• Cathode: Mercury (Hg) — Na deposits, forms Na-Hg amalgam
• Anode: Graphite — $Cl_{2}$ evolved
• Denuder chamber: 2Na(amalgam) + $2H_{2}O$ → 2NaOH + $H_{2}$ + Hg (Hg recycled)

Chlor-Alkali Process (modern alternative): $NaCl + H_2O \xrightarrow{electrolysis} NaOH + \frac{1}{2}Cl_2 + \frac{1}{2}H_2$

2. Sodium Carbonate ($Na_{2}CO_{3}$) — Washing Soda

Solvay Process (3 steps):

1. $NaCl + NH_3 + CO_2 + H_2O \rightarrow NaHCO_3\downarrow + NH_4Cl$ ($NaHCO_{3}$ precipitates — less soluble)
2. $2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + CO_2\uparrow + H_2O$
3. $2NH_4Cl + Ca(OH)_2 \rightarrow CaCl_2 + 2NH_3\uparrow + 2H_2O$ ($NH_{3}$ recycled)

Net reaction: 2NaCl + $CaCO_{3}$ → $Na_{2}CO_{3}$ + $CaCl_{2}$

3. Sodium Bicarbonate ($NaHCO_{3}$) — Baking Soda

• Prepared as intermediate in Solvay process
• Decomposition: $2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + CO_2 + H_2O$
• Uses: Antacid (neutralizes HCl), baking ($CO_{2}$ leavening), fire extinguisher

4. Sodium Chloride (NaCl) — Rock Salt

• From sea water evaporation or rock salt mining
• Feedstock for Castner-Kellner and Solvay processes
• Uses: Food preservation, chlor-alkali industry