Basics of Acids and Bases

Identification of Acids and Bases

• Acids: Typically have a hydrogen atom in front (e.g., HCl, HF, HC2H3O2).
• Bases: Often contain a hydroxide ion (e.g., NaOH, KOH).
• Hydrogen Position:
  • Attached to a metal (e.g., sodium hydride) = Base.
  • Attached to a non-metal = Acid.

Charge Characteristics

• Acids: Tend to be positively charged.
• Bases: Tend to be negatively charged.

Definitions

Arrhenius Definition

• Acids: Release H⁺ ions into solution, forming hydronium ions (H₃O⁺).
• Bases: Release hydroxide ions (OH⁻) into solutions.

Bronsted-Lowry Definition

• Acids: Proton donors.
• Bases: Proton acceptors.

Acid-Base Reactions

• Example: HCl (acid) + H₂O (base) → Cl⁻ (conjugate base) + H₃O⁺ (conjugate acid).
• Conjugate Pairs: Acid turns into conjugate base; base turns into conjugate acid.

pH Scale

• Scale ranges typically from 0 to 14.
• Neutral: pH = 7.
• Acidic: pH < 7.
• Basic: pH > 7.
• Equations:
  • pH = -log[H₃O⁺]
  • pOH = -log[OH⁻]
  • pH + pOH = 14 (at 25°C)
  • [H₃O⁺] = 10^(-pH)
  • [OH⁻] = 10^(-pOH)

Strength of Acids and Bases

• Strong Acids: Ionize completely (e.g., HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄).
• Weak Acids: Partially ionize.
• Strong Bases: Soluble ionic compounds that ionize completely (e.g., KOH, NaOH).
• Weak Bases: Include NH₃ and conjugate bases of weak acids.

Chemical Reactions

• Strong Acids: Use single arrow indicating complete ionization.
• Weak Acids: Use double arrow indicating partial ionization (equilibrium).

Acid and Base Mechanisms

• Oxide Ion Reaction: Produces hydroxide ions.
• Hydride Ion Reaction: Produces hydrogen gas and hydroxide.

Properties of Acids and Bases

• Acids: Taste sour, turn blue litmus paper red.
• Bases: Taste bitter, feel slippery, turn red litmus paper blue.

Conductivity

• Strong acids/bases: Strong electrolytes, conduct electricity well.
• Weak acids/bases: Weak electrolytes, conduct less electricity.

Reactions with Metals

• Acids: React with active metals to produce hydrogen gas.

Definitions Summarized

• Arrhenius: Acids release H⁺, bases release OH⁻.
• Bronsted-Lowry: Acids donate protons, bases accept protons.
• Lewis: Acids accept electron pairs, bases donate electron pairs.

Amphoteric Substances

• Substances like H₂O can act as either an acid or a base.

Equilibrium Constants

• Ka: Acid dissociation constant.
• Kb: Base dissociation constant.
• Kw: Water ionization constant, 1 x 10⁻¹⁴ at 25°C.

Calculations and Practice Problems

• Worked examples with calculations of pH, pOH, [H₃O⁺], [OH⁻], Ka, Kb, pKa, and pKb.

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Summary: The lesson covers the fundamental concepts of acids and bases, including their identification, properties, chemical reactions, and definitions based on different theories. It also explains acid and base strength, pH calculations, and equilibrium constants associated with acid-base reactions. Practical examples help reinforce the theoretical knowledge.