Acids, Bases, and Salts: Introduction to Acids

Definition of Acid

• Acid: A substance that donates H+ ions as the only positive charged ions in its aqueous solution.
• Cannot furnish other positive ions like Na+, K+, Ca2+, etc.
• H+ ions are unstable and combine with H2O to form H3O+ (hydronium ion).

Organic Acids

• Obtained from plants, animals, and other organic sources.
• Examples:
  • Acetic Acid (CH3COOH): Found in vinegar, used in cooking.
  • Formic Acid (HCOOH): Found in the sting of ants.
  • Lactic Acid: Present in milk.
  • Citric Acid: Found in oranges and other sour fruits.
  • Tartaric and Hydrazoic Acids: Used in cooking, derived from tamarind.

Weak and Strong Acids

• Weak Acids: Do not furnish a large amount of H+ ions in solution. Example: Organic acids like acetic acid.
• Strong Acids: Furnish a large amount of H+ ions. Example: Mineral acids like HCl, H2SO4, and HNO3.

Mineral Acids

• Derived from the earth, lab-produced.
• Important ones: Hydrochloric acid (HCl), Sulfuric acid (H2SO4), and Nitric acid (HNO3).
• Generally very strong, except Carbonic Acid (H2CO3), which is a weak mineral acid.

Basicity of Acids

• The number of ionizable H+ ions an acid molecule can furnish.
• Monobasic Acids: HCl, HNO3 (1 ionizable H+).
• Dibasic Acids: H2SO4, H2S2O3 (2 ionizable H+).
• Tribasic Acids: H3PO4 (3 ionizable H+).
• Basicity is determined by the structure and not merely by the number of hydrogen atoms.

Preparation of Acids

1. Direct Combination or Synthesis

• Nonmetal + Hydrogen -> Acid
• Examples: Cl2 + H2 -> HCl (gaseous, forms hydrochloric acid in water).

2. Dissolving Nonmetal Oxides in Water

• CO2 + H2O -> H2CO3 (Carbonic Acid)
• SO3 + H2O -> H2SO4 (Sulfuric Acid)

3. Oxidation of Nonmetals

• Using HNO3 as an oxidizing agent to form acids like H2SO4 (Sulfuric Acid) by oxidizing sulfur.

4. Preparation of Volatile Acids

• Involves the process of preparing HCl and HNO3 using a non-volatile acid like H2SO4 at temperatures below 200°C.

Key Point: Acids can be categorized into organic and mineral acids, with properties such as basicity and strength varying based on their composition and how they are prepared.