Overview
This lecture covers the main types of chemical reactions: synthesis, decomposition, combustion, single replacement, and double replacement reactions, including their general forms and key examples.
Synthesis (Combination) Reactions
- Multiple reactants combine to form a single product (A + B → AB).
- Example: Zinc + Oxygen → Zinc oxide.
- Example: Barium oxide + Carbon dioxide → Barium carbonate.
Decomposition Reactions
- A single compound breaks down into two or more products (AB → A + B).
- Example: Magnesium nitride decomposes on heating to Magnesium + Nitrogen gas.
- Example: Heating Calcium carbonate → Calcium oxide + Carbon dioxide.
Combustion Reactions
- Involves reaction of a hydrocarbon (CxHy or CxHyOz) with oxygen to yield carbon dioxide and water.
- Example: Propane + Oxygen → Carbon dioxide + Water.
- Example: Ethanol + Oxygen → Carbon dioxide + Water (with enough oxygen present).
- Combustion reactions are highly exothermic (release heat energy).
Single Replacement Reactions
- An element replaces another in a compound (A + BC → AC + B).
- Metal replaces metal: Zinc + Copper(II) chloride → Zinc chloride + Copper.
- Non-metal replaces non-metal: Bromine + Sodium iodide → Sodium bromide + Iodine.
Double Replacement Reactions
- Two compounds exchange partners (AB + CD → AD + CB).
- Example: Calcium chloride + Sodium nitrate → Calcium nitrate + Sodium chloride.
- Cations pair with a different anion, and vice versa.
- Ions with opposite charges attract; like charges do not pair.
Special Double Replacement Reactions
- Precipitation Reaction: Mixing solutions forms an insoluble solid (precipitate), e.g., Calcium nitrate + Sodium phosphate → Sodium nitrate + Calcium phosphate (solid).
- Gas Evolution Reaction: Produces a gas, e.g., Sodium sulfide + Hydrochloric acid → Sodium chloride + Hydrogen sulfide (gas).
- Acid-Base Neutralization: Acid and base form water and a salt, e.g., Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water.
Key Terms & Definitions
- Synthesis Reaction — Multiple reactants form one product.
- Decomposition Reaction — One reactant breaks into multiple products.
- Combustion Reaction — Hydrocarbon reacts with oxygen to produce CO₂ and H₂O.
- Single Replacement Reaction — An element replaces another in a compound.
- Double Replacement Reaction — Two compounds exchange ions to form new compounds.
- Precipitation Reaction — A double replacement reaction forming a solid product.
- Gas Evolution Reaction — A reaction that produces a gas product.
- Acid-Base Neutralization — Acid and base react to form water and a salt.
Action Items / Next Steps
- Review examples of each reaction type.
- Practice writing and balancing equations for all five reaction types.