When water is poured on calcium oxide (CaO), a vigorous exothermic reaction takes place, producing calcium hydroxide (Ca(OH)₂).
Chemical Reaction:
CaO + H₂O → Ca(OH)₂ + Heat
What Happens in the Reaction:
- Calcium oxide (also called quicklime) reacts rapidly with water.
- A large amount of heat is released, making it an exothermic reaction.
- The product formed is calcium hydroxide, also known as slaked lime.
- The mixture may become hot enough to boil or produce steam.
Observations:
- Hissing sound may be heard
- Temperature increases significantly
- A white, powdery or paste-like substance is formed
Real-Life Applications:
- Used in whitewashing walls
- Preparation of mortar and cement
- Neutralizing acidic soils in agriculture
Safety Note:
- This reaction is highly exothermic, so it should be handled carefully to avoid burns.
Key Concept (for exams):
- CaO + H₂O → Ca(OH)₂ is an exothermic combination reaction.