Yes, calcium oxide reacts vigorously with water.
Calcium oxide (CaO), commonly known as quicklime, undergoes a significant and highly exothermic chemical reaction when it comes into contact with water (H₂O). This vigorous interaction results in the formation of calcium hydroxide (Ca(OH)₂), also known as slaked lime, and is accompanied by a substantial liberation of heat. This chemical transformation is famously referred to as the slaking of lime.
The Vigorous Reaction of Quicklime with Water
When solid calcium oxide is introduced to water, a rapid and noticeable reaction begins. The quicklime absorbs water, swells, and then crumbles into a fine, white powder of calcium hydroxide. The energy released during this process is considerable, often causing the mixture to heat up significantly, sometimes even reaching temperatures high enough to boil the water. This strong exothermic nature makes the reaction of quicklime with water a fascinating and useful industrial process.
Understanding the Chemistry: Quicklime to Slaked Lime
The chemical equation for this reaction is straightforward:
CaO(s) + H₂O(l) → Ca(OH)₂(s) + Heat
Here's what each component represents:
- CaO(s): Calcium oxide in its solid state (quicklime).
- H₂O(l): Water in its liquid state.
- Ca(OH)₂(s): Calcium hydroxide in its solid state (slaked lime).
- Heat: Represents the energy released, indicating an exothermic reaction.
This reaction is a classic example of a combination reaction where two or more reactants combine to form a single product. The robust nature of this reaction is primarily due to the strong affinity of calcium oxide for water.
Key Properties of Reactants and Products
Understanding the properties of the substances involved helps to appreciate the reaction's significance.
| Property | Calcium Oxide (Quicklime) | Calcium Hydroxide (Slaked Lime) | Water |
|---|---|---|---|
| Chemical Formula | CaO | Ca(OH)₂ | H₂O |
| State (25°C) | Solid | Solid | Liquid |
| Appearance | White, caustic, crystalline solid | White, powdery solid (often suspended in water as "milk of lime") | Clear, odorless liquid |
| Reactivity with Water | Highly vigorous, exothermic, forms Ca(OH)₂ | Sparingly soluble, forms an alkaline solution (lime water) | Reacts readily with CaO, acts as a solvent |
| Common Names | Quicklime, Burnt Lime | Slaked Lime, Hydrated Lime | - |
Practical Insights and Applications of Slaked Lime
The product of this reaction, calcium hydroxide (slaked lime), is a versatile chemical with numerous industrial and everyday applications. Its mild alkalinity and low solubility make it valuable in various fields.
Some key applications include:
- Agriculture: Used to neutralize acidic soils, improving crop yields. This process is known as liming. Learn more about agricultural lime.
- Water Treatment: Acts as a flocculant in water purification, helping to remove impurities by causing them to clump together. It also helps in pH adjustment. Discover its role in water purification.
- Construction: A crucial component in making mortar, plaster, and cement. It provides binding properties and contributes to strength.
- Environmental Control: Employed in flue gas desulfurization to remove sulfur dioxide from industrial emissions, helping to reduce air pollution.
- Chemical Industry: Used in the manufacture of various chemicals, including bleach and sugar refining.
Safety Considerations When Handling Quicklime
Due to its vigorous reaction with water and its caustic nature, quicklime requires careful handling:
- Heat Release: The exothermic reaction can cause burns, so skin contact during slaking should be avoided.
- Irritant: Quicklime is an irritant to skin, eyes, and the respiratory system. Always wear appropriate personal protective equipment (PPE) such as gloves, eye protection, and a dust mask.
- Storage: Store quicklime in dry, airtight containers to prevent accidental reaction with atmospheric moisture.
Conclusion
The reaction between calcium oxide and water is a fundamental chemical process, yielding calcium hydroxide and releasing significant heat. This transformation is not only chemically interesting but also forms the basis for numerous practical applications across various industries.
