Overview

This topic explores the major types of chemical reactions and the principles of oxidation-reduction (redox) chemistry. You'll learn to classify reactions, identify electron transfers, and balance redox equations—skills essential for understanding how chemical transformations occur in both laboratory and real-world processes.

Key Concepts and Structures

• Synthesis (Combination) Reactions: Two or more reactants combine to form one product. Think of it as construction—small parts come together to build something larger.
  A + B → AB
• Decomposition Reactions: A single compound breaks apart into simpler substances. The opposite of synthesis.
  AB → A + B
• Single Replacement Reactions: One element swaps places with another in a compound. Use the activity series to predict if it will occur.
  A + BC → B + AC
• Double Replacement (Metathesis) Reactions: Two compounds exchange ions to form two new compounds. Often forms a precipitate or gas.
  AB + CD → AD + CB
• Combustion Reactions: A hydrocarbon reacts with oxygen to produce carbon dioxide and water. Always exothermic.
  CₓHᵧ + O₂ → CO₂ + H₂O
• Acid–Base Reactions: A proton (H⁺) is transferred from an acid to a base. Can be classified under double replacement but involves neutralization.
• Precipitation Reactions: A type of double replacement where an insoluble solid (precipitate) forms from two aqueous solutions.
• Redox Reactions: Involve transfer of electrons. Key ideas:
  • Oxidation: Loss of electrons (oxidation number increases)
  • Reduction: Gain of electrons (oxidation number decreases)
  • Oxidizing Agent: Accepts electrons (gets reduced)
  • Reducing Agent: Donates electrons (gets oxidized)
• Balancing Redox Equations: Use the half-reaction method. In acidic solutions, use H⁺ and H₂O; in basic solutions, add OH⁻ as needed. Ensure mass and charge are balanced.
• Activity Series: A ranked list of metals by reactivity. Helps predict whether a single replacement reaction will occur.

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