Calcium oxide, also known as quicklime, is a white, alkaline substance with a high melting point. It reacts vigorously with water to produce calcium hydroxide and generates significant heat. It is used in various industrial applications, including cement manufacturing, agriculture, and water treatment.
| IUPAC Name | Calcium oxide |
| Molecular Formula | CaO |
| CAS Number | 1305-78-8 |
| Synonyms | Quicklime; Burnt lime; Lime; Calx; Unslaked lime; Calcium(II) oxide; Calcia; Lime pebble; Lime rock; Calcium monoxide; Lime flux |
| InChI | InChI=1S/Ca.O |
Calcium Oxide Properties
Calcium Oxide Formula
The chemical formula of Calcium Oxide is CaO, indicating that it contains one Calcium cation (Ca2+) and one Oxide anion (O2-). The formula of Calcium Oxide reflects its ionic nature, where Calcium cations and Oxide anions are held together by strong electrostatic forces. The formula of Calcium Oxide is used to identify the compound in various chemical reactions and to calculate its molecular weight and other physical properties.
Calcium Oxide Molar Mass
The molar mass of Calcium Oxide, also known as quicklime, is 56.077 grams per mole. It is derived from the atomic weight of Calcium (40.078 g/mol) and Oxygen (15.999 g/mol) which make up the compound. The molar mass of Calcium Oxide is used in various calculations, such as determining the amount of reactant needed to produce a specific amount of product or calculating the concentration of a solution.
Calcium Oxide Boiling Point
Calcium Oxide does not have a boiling point since it undergoes thermal decomposition at high temperatures instead of boiling. At temperatures above 2572 °C, Calcium Oxide dissociates into Calcium and Oxygen. However, the thermal decomposition of Calcium Oxide can be used to produce Calcium Oxide with higher purity and reactivity for industrial applications.
Calcium Oxide Melting Point
The melting point of Calcium Oxide is 2572 °C, making it a high melting point substance. It has a high melting point due to its ionic nature, where Calcium cations and Oxide anions are held together by strong electrostatic forces. The high melting point of Calcium Oxide also makes it useful in high-temperature applications such as in the manufacturing of steel and cement.
Calcium Oxide Density g/ml
The density of Calcium Oxide varies depending on its crystalline structure and purity. The typical density of Calcium Oxide is 3.35 g/mL for the bulk material, while the theoretical density is 3.50 g/mL. The low density of Calcium Oxide is due to its porous structure, which allows it to absorb moisture from the air and increase its weight and volume.
Calcium Oxide Molecular Weight
The molecular weight of Calcium Oxide, also known as formula weight or molar mass, is 56.077 grams per mole. It is calculated by adding the atomic weights of Calcium and Oxygen, which make up the compound. The molecular weight of Calcium Oxide is used in various calculations, such as determining the amount of reactant needed to produce a specific amount of product or calculating the concentration of a solution.
Calcium Oxide Structure
Calcium Oxide has a cubic crystal structure, where Calcium cations and Oxide anions are arranged in a face-centered cubic lattice. The crystal structure of Calcium Oxide is similar to that of Sodium Chloride and other ionic compounds. The ionic nature of Calcium Oxide makes it a good electrical insulator and an important material in the manufacturing of electronic components.
| Appearance | White, odorless solid |
| Specific Gravity | 3.35 g/cm³ |
| Color | White |
| Odor | Odorless |
| Molar Mass | 56.077 g/mol |
| Density | 3.35 g/cm³ |
| Melting Point | 2572 °C |
| Boiling Point | Does not boil, undergoes thermal decomposition |
| Flash Point | Not applicable |
| Water Solubility | Reacts with water to form Calcium Hydroxide |
| Solubility | Insoluble in water, soluble in acid |
| Vapour Pressure | Negligible |
| Vapour Density | Not applicable |
| pKa | Not applicable |
| pH | 12-13 |
Calcium Oxide Safety and Hazards
Calcium Oxide, also known as quicklime, is a highly reactive and caustic substance that poses several hazards to human health and the environment. It can cause severe irritation and burns to the skin, eyes, and respiratory system if not handled properly. Inhaling quicklime dust or vapors can cause respiratory distress, coughing, and shortness of breath. It is also highly reactive with water and can release large amounts of heat, leading to steam burns and explosions. quicklime should be stored in a cool, dry, and well-ventilated area, away from incompatible substances. Proper protective equipment and handling procedures should be followed to prevent accidents and exposure.
| Hazard Symbols | Corrosive (C) |
| Safety Description | Wear protective gloves, clothing, and eye/face protection. Handle and store with care. Avoid inhalation, ingestion, and contact with skin and eyes. |
| UN IDs | UN1910 |
| HS Code | 2522.20.00 |
| Hazard Class | 8 – Corrosive substances |
| Packing Group | II |
| Toxicity | Highly toxic |
Calcium Oxide Synthesis Methods
Thermal decomposition of limestone, the reaction of calcium hydroxide with heat, and electrolysis of calcium chloride synthesize Calcium Oxide or quicklime.
The most common method for synthesizing quicklime is by heating limestone to a high temperature of about 900-1000°C in a lime kiln. This process, known as calcination, releases carbon dioxide and leaves behind quicklime. Processing and grinding the quicklime produces a fine powder for multiple applications.
Another method for synthesizing quicklime involves heating Calcium Hydroxide, also known as slaked lime, to a high temperature. This process, known as dehydroxylation, also releases water and leaves behind quicklime.
Electrolysis of Calcium Chloride is a less common method for synthesizing quicklime. Dissolve Calcium Chloride in water and pass an electrical current through the solution to generate quicklime and chlorine gas.
Calcium Oxide Uses
Calcium Oxide, also known as quicklime, has numerous uses in various industries due to its unique properties. Some of its major uses are:
- Steel production: Used as a fluxing agent in steel production, where it helps to remove impurities and improve the quality of the steel.
- Water treatment: Used in water treatment to remove impurities and adjust the pH of water.
- Agriculture: Used in agriculture as a soil amendment to adjust the pH of the soil and provide essential nutrients to plants.
- Chemical industry: Used in the production of chemicals such as calcium carbide, calcium hypochlorite, and calcium stearate.
- Construction: Used in the construction industry as a component of cement, mortar, and plaster.
- Food industry: Used in the food industry as a firming agent and acidity regulator.
- Paper industry: Used in the paper industry as a component of the white liquor used in the kraft pulping process.
- Petroleum industry: Used in the petroleum industry as a catalyst in the refining process.
Questions:
Q: What is the formula for calcium oxide?
A: The formula for calcium oxide is CaO.
Q: What is the oxidation number of calcium?
A: The oxidation number of calcium in Calcium Oxide is +2.
Q: Is calcium oxide ionic or covalent?
A: Calcium Oxide is an ionic compound, consisting of positively charged calcium ions and negatively charged oxide ions.
Q: Is calcium oxide a solid?
A: Yes, Calcium Oxide is a solid at room temperature and standard pressure. It has a white or grayish-white appearance and is highly reactive.