Ethanoic Acid (Acetic Acid)

📚 Key Concepts

🔹 Real-Life Example

When wine or fruit juice is left open, it turns sour due to the formation of ethanoic acid through fermentation. This is the same acid that gives vinegar its characteristic taste and smell. Ancient civilizations used this natural process to preserve food!

🧪 Properties of Ethanoic Acid

🔸 Physical Properties

  • Molecular formula: CH₃COOH
  • Appearance: Colorless liquid
  • Odor: Pungent, vinegar-like smell
  • Freezing point: 17°C (pure acid called glacial acetic acid)
  • Miscibility: Completely miscible with water

🔸 Chemical Properties

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Acidic Nature: CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺ (Partially ionizes – weak acid)

Reactions:

  • With metals: 2CH₃COOH + Zn → (CH₃COO)₂Zn + H₂↑
  • With bases: CH₃COOH + NaOH → CH₃COONa + H₂O
  • With carbonates: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂↑ + H₂O

🧪 Preparation Methods

🔸 Industrial Methods

1. Fermentation Process: C₂H₅OH + O₂ → CH₃COOH + H₂O (Ethanol oxidized by bacteria in presence of air)

2. Carbonylation of Methanol: CH₃OH + CO → CH₃COOH (High pressure, catalyst required)

🧪 Uses of Ethanoic Acid

  • Food industry: Vinegar (5-8% solution)
  • Preservation: Pickles, chutneys
  • Chemical industry: Manufacturing acetates, plastics
  • Medical: Antiseptic properties
  • Laboratory: Common reagent

🔍 Advanced: Vinegar Production

Commercial vinegar production involves two-stage fermentation:

  1. Sugar → Ethanol (alcoholic fermentation)
  2. Ethanol → Acetic acid (acetic fermentation)