Lecture Notes: Acids, Bases, and Salts

1. Introduction to Acids and Bases

• Acids
  • Sour in taste.
  • Common examples:
    • Curd (Lactic Acid)
    • Lemon (Citric Acid)
    • Vinegar (Acetic Acid)
• Bases
  • Bitter in taste and soapy to touch.
  • Found in: Detergents, Toothpaste, Hair dyes.

2. Testing Acids and Bases

• Acid-Base Indicators
  • Natural Indicators
    • Litmus: Blue turns red in acids; Red turns blue in bases.
    • Others: Red cabbage, Turmeric, Hibiscus.
  • Synthetic Indicators
    • Methyl Orange: Red in acids, Yellow in bases.
    • Phenolphthalein: Colorless in acids, Pink in bases.
  • Olfactory Indicators
    • Examples: Onion, Vanilla essence, Clove oil.
    • Onion loses smell in the presence of bases.

3. Reactions Involving Acids and Bases

• With Metals
  • Acids react with metals to form salt + hydrogen gas.
  • Bases react with certain metals to form salt + hydrogen gas.
• With Metal Carbonates and Bicarbonates
  • Reaction with acids forms salt, water, and carbon dioxide.
• Neutralization Reaction
  • Acid + Base → Salt + Water.
  • Example: Sodium hydroxide and hydrochloric acid.
• With Metal and Non-metal Oxides
  • Acids with metal oxides form salt + water.
  • Bases with non-metallic oxides form salt + water.

4. Conductivity of Acids and Bases

• Acids and bases conduct electricity when dissolved in water due to ion formation.

5. Dilution of Acids and Bases

• Adding water decreases ion concentration, releasing heat.
• Always add acid to water, not vice versa.

6. Strength of Acids and Bases

• pH Scale: Measures strength from 0 to 14.
  • pH 7: Neutral
  • pH < 7: Acidic
  • pH > 7: Basic

7. Importance of pH

• In Nature
  • Essential for aquatic life and plant growth.
  • Acid rain affects water bodies.
• In Human Body
  • Stomach acidity, antacids use (e.g., magnesium hydroxide).
  • Tooth enamel and decay prevention.

8. Self-Defense Mechanisms

• Organisms use acids/bases for defense (e.g., bee stings).

9. Salts

• Nature of Salts
  • Can be neutral, acidic, or basic based on their pH.
• Common Salt (Sodium Chloride)
  • Utilized in making various compounds like caustic soda, baking soda.

10. Important Compounds

• Manufacture and Uses
  • Sodium Hydroxide: Chlor-Alkali process.
  • Baking Soda (NaHCO3)
  • Washing Soda (Na2CO3): Recrystallization.
  • Bleaching Powder (CaOCl2): Made from calcium hydroxide and chlorine.
  • Plaster of Paris (CaSO4·1/2H2O): From gypsum.

End of Notes

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