Calcium hydroxide, also known as slaked lime or hydrated lime, is a widely used chemical compound with the formula Ca(OH)₂. This article delves into its chemical formula, key properties, and diverse applications across various industries.
Understanding the Chemical Formula: Ca(OH)₂
The chemical formula Ca(OH)₂ represents the composition of calcium hydroxide. It indicates that one molecule of calcium hydroxide contains one calcium atom (Ca) bonded to two hydroxide ions (OH). The hydroxide ion carries a negative charge, balanced by the positive charge of the calcium ion. This ionic bonding is crucial to understanding its properties.
Key Properties of Calcium Hydroxide
Calcium hydroxide exhibits several important properties that contribute to its widespread use:
Physical Properties:
- Appearance: White crystalline powder
- Solubility: Slightly soluble in water, forming an alkaline solution called limewater.
- Melting Point: 580 °C (1076 °F)
- Density: 2.211 g/cm³
Chemical Properties:
- Alkalinity: It's a strong base, readily accepting protons (H⁺).
- Reactivity: Reacts with acids to form salts and water (neutralization reaction).
- Dehydration: At high temperatures, it can lose water to form calcium oxide (CaO), also known as quicklime.
Production of Calcium Hydroxide
Calcium hydroxide is primarily produced through a process called slaking. This involves reacting calcium oxide (quicklime) with water:
CaO(s) + H₂O(l) → Ca(OH)₂(aq)
This reaction is highly exothermic, meaning it releases a significant amount of heat.
Applications of Calcium Hydroxide
The versatility of calcium hydroxide makes it essential in numerous applications:
1. Construction and Building Materials:
- Mortar and Plaster: A key component, providing strength and setting properties.
- Concrete: Improves workability and strength.
- Limewash: Used as a traditional building paint.
2. Water Treatment:
- pH Adjustment: Increases the pH of acidic water.
- Phosphate Removal: Used in wastewater treatment to remove excess phosphate.
3. Agriculture:
- Soil Amendment: Increases soil pH, benefiting certain crops.
- Nutrient Delivery: Calcium is an essential nutrient for plants.
4. Food Industry:
- Food Additive: Used as a firming agent, stabilizer, and pH adjuster in various foods (E526).
- Sugar Refining: Used in the purification of sugar.
5. Other Industrial Applications:
- Paper Production: Used in the pulping process.
- Chemical Synthesis: Used as a reactant in various chemical processes.
Safety Precautions
While generally safe when handled correctly, calcium hydroxide can cause skin and eye irritation. Always wear appropriate personal protective equipment (PPE), such as gloves and eye protection, when handling this chemical. If contact occurs, immediately flush the affected area with plenty of water.
Conclusion
Calcium hydroxide, with its simple yet powerful chemical formula Ca(OH)₂, plays a crucial role in various aspects of modern life. Its diverse properties and applications make it a valuable chemical compound across numerous industries, from construction to food processing.
