Lecture Notes: Chemical Reactions and Ionic Equations

Key Concepts

• Chemical Reaction Demonstrated:
  • Lead(II) nitrate + 2 potassium iodide → Lead(II) iodide + 2 potassium nitrate
  • Exchange of negative ions (NO3- and I-) occurs.
• Complete Ionic Equation:
  • Pb2+ + 2 NO3- + 2 K+ + 2 I- → PbI2 + 2 K+ + 2 NO3-
• Net Ionic Equation:
  • Cancel out spectator ions (2 NO3- and 2 K+).
  • Resulting equation: Pb2+ + 2 I- → PbI2 (solid)

Reaction Observation

• Visual Change:
  • Colorless solutions of Pb2+ and 2 I- react to form a deep yellow precipitate of PbI2.
  • Reaction driven by formation of solid precipitate.

Predicting Reactions

• Importance of Solubility Rules:
  • Solubility rules help predict if a reaction occurs without experimentation.
  • Key rules: Lead(II) halides are generally insoluble; all nitrates are soluble.
• Prediction Process:
  1. Identify Ions in Solution:
     • Before reaction: Pb2+, NO3-, K+, I-
  2. Check Solubility:
     • Solubility rules indicate that Pb2+ and I- will form insoluble PbI2.

Examples

Example 1: Sodium Carbonate and Calcium Perchlorate

• Ions Present: Na+, CO3 2-, Ca2+, ClO4-
• Solubility Check:
  • Calcium carbonate (CaCO3) is insoluble.
• Net Ionic Equation:
  • Ca2+ + CO3 2- → CaCO3 (solid)

Example 2: Barium Nitrate and Calcium Chloride

• Ions Present: Ba2+, NO3-, Ca2+, Cl-
• Solubility Check:
  • All ion combinations are soluble; no reaction occurs.