Yes, calcium oxide (also known as lime or quicklime) is sparingly soluble in water. While it does dissolve to a certain extent, it is more notably characterized by its vigorous chemical reaction with water, a process often referred to as "slaking."
Understanding Calcium Oxide's Interaction with Water
Calcium oxide is a hard, white or grayish-white porous solid, commonly found as pebbles or powder. When it encounters water, two main phenomena occur:
- Dissolution: A small amount of calcium oxide dissolves physically into the water, forming a solution.
- Chemical Reaction (Slaking): More significantly, calcium oxide reacts exothermically with water to form calcium hydroxide, also known as slaked lime. This reaction is quite rapid and releases a substantial amount of heat, which is why it's often described as "quick slaking."
Detailed Solubility Data
The degree to which calcium oxide dissolves in water is relatively low and is influenced by temperature. Higher temperatures actually decrease its solubility.
| Temperature | Solubility in Water |
|---|---|
| 25°C (Room Temperature) | 1 gram per 840 ml |
| 100°C (Boiling Point) | 1 gram per 1,740 ml |
This data indicates that at room temperature, it takes 840 milliliters of water to dissolve just 1 gram of calcium oxide, making it significantly less soluble than many common salts. For comparison, sodium chloride (table salt) dissolves at a rate of about 359 grams per liter (1000 ml) at 25°C.
Practical Implications
The unique solubility and reactivity of calcium oxide have various industrial and environmental applications:
- Construction: Slaked lime (calcium hydroxide), formed from calcium oxide and water, is a key component in mortars, plasters, and cements. Its low solubility is advantageous for creating durable building materials. Learn more about calcium oxide on Wikipedia.
- Water Treatment: Calcium oxide and its derivatives are used to adjust the pH of water, remove impurities, and soften water. The controlled addition allows for precise treatment without excessive dissolution.
- Agriculture: It's used to reduce soil acidity, improving crop yield. Its sparing solubility ensures a gradual release into the soil.
- Chemical Industry: It serves as a flux in steel manufacturing and as a raw material for various chemicals.
Despite its limited physical dissolution, the chemical reaction with water is a defining characteristic of calcium oxide, making it a highly versatile compound across many sectors.
