Notes on Chemical Reactions

4.1 Introduction for Reactions

• Physical vs. Chemical Changes:
  • Physical Change: No change in composition; involves breaking/forming intermolecular attractions.
    • Example: Melting ice, boiling water, dissolving NaCl.
  • Chemical Change: Change in composition; involves breaking/forming bonds.
    • Example: Electrolysis of water, rusting of iron.

4.2 Net Ionic Equations

• Concept: Shows only the chemical species that are involved in a reaction, excluding spectator ions.
• Complete Ionic Equation: Includes all ions present.
• Net Ionic Equation: Excludes spectator ions.
• Examples:
  • Dissociation of NaCl in water.
  • Precipitation reactions.

4.3 Representations of Reactions

• Balanced Equations: Must conserve mass and charge.
• Particulate Representations: Visual models of reactions showing initial reactants and final products.

4.4 Physical and Chemical Changes: Recap and Problems

• Indicators of Chemical Change: Gas production, precipitate formation, energy release.

4.5 Stoichiometry

• Mole Relationships: Derived from balanced chemical equations to perform calculations.
• Limiting Reactants: Determine the amount of product formed.
• Calculation Examples:
  • MgCl2 + NaOH Reaction: Doubling reactants to increase product.

4.6 Introduction to Titration

• Process: Determining concentration by adding a titrant to a known volume until the reaction reaches the equivalence point.
• Indicators: Color changes to signal endpoint.
• Types:
  • Acid-Base Titrations
  • Red-Ox Titrations

4.7 Types of Chemical Reactions

• Categories:
  • Acid-Base Reactions: Involving H+ and OH- ions.
  • Red-Ox Reactions: Involving electron transfer.
  • Precipitation Reactions: Form insoluble solids from ions.

4.8 Introduction to Acid-Base Reactions

• Arrhenius Definition: Acids increase H+ ions, bases increase OH- ions in water.
• Brønsted-Lowry Definition: Acids donate protons, bases accept protons.
• Conjugate Acid-Base Pairs: Differ by one proton.

4.9 Oxidation-Reduction (Redox) Reactions

• Oxidation Numbers: Used to identify oxidized and reduced species.
• Redox Equations: Balance through electron transfer.
• Example: Al + Ag+ reaction.

Practice Problems

• Provided for each section to reinforce understanding through application.