NaOH (caustic soda): Manufactured by Castner-Kellner process (electrolysis of brine with Hg cathode, forms Na-Hg amalgam, then reacts with water). White deliquescent solid, strong base. Reacts with CO2: NaOH + CO2 → Na2CO3; 2NaOH + CO2 (excess) → Na2CO3 + H2O. Na2CO3 (washing soda): Solvay process — NaCl + NH3 + CO2 + H2O → NaHCO3 (precipitates, less soluble) → heated to Na2CO3 + H2O + CO2. Solvay process cannot make K2CO3 (KHCO3 is too soluble to precipitate). Na2CO3.10H2O is washing soda; loses water stepwise. NaHCO3 (baking soda): Mild base, decomposes on heating (2NaHCO3 → Na2CO3 + H2O + CO2). Used in fire extinguishers, antacids, baking powder (NaHCO3 + tartaric acid).