Soda production
Soda, Na₂CO₃, is widely used in glass, soap, paper, textiles, the oil industry and daily life, but it is rare in nature, so it is synthesised. Anhydrous Na₂CO₃ is calcined soda, Na₂CO₃·10H₂O (M = 286 g/mol) is crystalline or washing soda, NaHCO₃ is baking soda and NaOH is caustic soda — these are different substances. In the Leblanc (sulfate) process table salt is converted to Na₂SO₄ with sulfuric acid, reduced with coal to Na₂S, and Na₂S is heated with limestone to give soda: 2NaCl + H₂SO₄ → Na₂SO₄ + 2HCl, Na₂SO₄ + 2C → Na₂S + 2CO₂, Na₂S + CaCO₃ → Na₂CO₃ + CaS; it was costly and was displaced. In the Solvay (ammonia) process a saturated NaCl solution is saturated with ammonia and carbon dioxide, and sparingly soluble NaHCO₃ precipitates: NaCl + NH₃ + CO₂ + H₂O → NaHCO₃↓ + NH₄Cl; heating it gives soda: 2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O. Ammonia is regenerated from NH₄Cl with slaked lime: 2NH₄Cl + Ca(OH)₂ → 2NH₃ + CaCl₂ + 2H₂O, and CO₂ comes from roasting limestone, which makes the process economical. The Kungrad Soda Plant in Karakalpakstan produces various soda products.
“Sort the sodas”: cards show Na₂CO₃, Na₂CO₃·10H₂O, NaHCO₃, NaOH and the names (calcined, crystalline, baking, caustic) with uses. Teams match them up. Reminder: caustic soda and washing soda can harm skin and eyes; only adults handle them.