Types of Chemical Reactions – Combination Reactions
📚 Key Concepts
🔹 Real-Life Example
When you burn magnesium ribbon, it produces a brilliant white light and forms a white powder (magnesium oxide). The magnesium metal combines with oxygen from the air to form a single product. This is like two people joining hands to become a couple – two separate entities becoming one unit.
Combination Reaction: Reactions in which two or more reactants combine to form one product are called combination reactions.
🧪 Important Formulas
🔸 General Formula
A + B → AB
Where A and B are reactants, and AB is the single product.
🔸 Examples
- Mg + O₂ → 2MgO (Magnesium + Oxygen → Magnesium oxide)
- C + O₂ → CO₂ (Carbon + Oxygen → Carbon dioxide)
- CaO + H₂O → Ca(OH)₂ (Calcium oxide + Water → Calcium hydroxide)
🔹 Characteristics
- Two or more reactants form one product
- Usually exothermic (release energy)
- Energy in the form of heat or light is often released
- Also called synthesis reactions
🔍 Advanced: Energy Considerations
Most combination reactions are exothermic because when atoms bond together, they release energy. This is why burning (combustion) reactions, which are combination reactions with oxygen, produce heat and light.