Important Salts
Chemistry · महत्वपूर्ण लवण
📋Quick Overview
Salts are formed when an acid reacts with a base (Neutralization: Acid + Base → Salt + Water). Many salts are used in daily life and industry. The most important salts for exams are: Common salt (NaCl), Caustic soda (NaOH), Washing soda (Na₂CO₃), Baking soda (NaHCO₃), Bleaching powder (CaOCl₂), and Plaster of Paris (CaSO₄·½H₂O).
📖Important Salts — Detailed Table
| Salt | Formula | Preparation | Uses |
|---|---|---|---|
| Common Salt (NaCl) | NaCl | Evaporation of sea water; rock salt mining | Cooking, preserving food, making NaOH, Na₂CO₃, NaHCO₃ |
| Caustic Soda (NaOH) | NaOH | Chlor-alkali process: 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂ (electrolysis of brine) | Soap making, paper, petroleum refining, degreasing |
| Washing Soda (Na₂CO₃·10H₂O) | Na₂CO₃·10H₂O | Solvay process: NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ (then heat to Na₂CO₃) | Cleaning, glass making, softening hard water, paper industry |
| Baking Soda (NaHCO₃) | NaHCO₃ | NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ + NH₄Cl | Baking (leavening agent), fire extinguisher, antacid, soda water |
| Bleaching Powder (CaOCl₂) | CaOCl₂ | Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O (slaked lime + chlorine gas) | Bleaching clothes/textiles, water purification, disinfection |
| Plaster of Paris (POP) | CaSO₄·½H₂O | Heat Gypsum at 373K: CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O | Plastering walls, setting broken bones, making toys/statues, chalk |
📖Chlor-Alkali Process — Products
- •Electrolysis of brine (NaCl solution) produces THREE useful products:
- •At Cathode (−): NaOH (Sodium Hydroxide/Caustic Soda) + H₂ gas
- •At Anode (+): Cl₂ gas (Chlorine)
- •H₂ gas → used in fuels, hydrogenation of oils (vanaspati ghee)
- •Cl₂ gas → water purification, PVC, pesticides, disinfectant
- •NaOH → soaps, detergents, paper, aluminium extraction
📖POP Setting Reaction
- •When water is added to POP, it sets into a hard solid (Gypsum): CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O (exothermic, becomes hot)
- •POP expands slightly on setting → perfect for casts (no gaps)
- •Should be stored in moisture-proof containers (or it becomes useless)