Calcium Oxide

Calcium oxide (CaO) is a colourless, cubic crystalline as well as white amorphous chemical compound. Although it is also known as lime, quicklime, or caustic lime, commercial lime frequently contains impurities such as silica, iron, alumina, and magnesia. It is made by heating calcium carbonate (– for example, limestone) to 500°C to 600°C in a special lime kiln and decomposing it into oxide as well as carbon dioxide. Calcium oxide is widely used in industry, for example, in the production of porcelain and glass, in the purification of sugar, in the preparation of bleaching powder, calcium carbide, and calcium cyanamide, in water softeners, and in mortars and cements. It is used in agriculture to treat acidic soils (liming). When exposed  to high temperatures, it becomes incandescent.

Physical properties of calcium oxide

• Calcium oxide has a high surface tension, a medium flowability, and a high to intermediate contractility and expansion rate. 

• Calcium oxide is not volatile at ceramic temperatures. 

• Calcium oxide has a moderate effect on colour, but in large quantities, it has a bleaching effect on iron oxide. 

• It is also available in tomato reds and khaki. 

• It is crystalline, alkaline, caustic, and white solid at room temperature.

Reaction of calcium oxide

Calcium carbonate (mineral calcite; CaCO3) is found in materials such as seashells and limestone, as well as the thermal decomposition of these materials can result in calcium oxide in a lime kiln.

Calcination is the process by which burnt lime is prepared. At extreme temps, the reactants are thermally decomposed while the temperature remains below the melting point.

The temperature range for calcination of calcium carbonate is 1070-1270 0 C. Typically, these reactions occur in a rotary kiln, and the products and outcomes of those reactions are carbon dioxide and burnt lime. Following Le- Chatelier’s  principle, carbon dioxide is removed instantly, allowing the reaction to be preceded until the process is completed.

CaCO3  CaO + CO2

A reaction like this in nature is exothermic and reversible in the forward direction.

Formula for Lime Water

Calcium hydroxide is the chemical name for lime water, and its chemical formula is Ca(OH)2. When water is added to lime, the following reaction occurs: the formation of calcium hydroxide Ca(OH)2.

CaO + H2O  Ca (OH)2

It is a very strong and exothermic reaction that results in the formation of steam clouds.

In nature, it is a basic oxide that produces salts when it comes into contact with an acid. It forms a cubic crystal lattice when it crystallises. The standard molar entropy of calcium oxide is 40 joules per mole Kelvin. An intense glow is produced when it is subjected to heat to temperatures greater than 2500 C.

CaO+H2SO4  CaSO4+H2O 

Types of Calcium oxide

Calcium oxide, as it is used in construction products, is broadly classified into three types:

• Pure is another word for fat, rich, air, slaked, slack, pickling, hydrated, and high-calcium lime. It is primarily composed of calcium hydroxide and may contain up to 5% other ingredients.

• Hydraulic – Also known as water lime. It is made of lime, silica, and/or alumina, and hardens when exposed to water. It has the ability to be set underwater.

• Poor lime is also referred to as lean lime or meagre lime. Poor lime sets and cures slowly and has a low strength.

Usage of Calcium oxide

The primary application of quicklime is in the production of basic oxygen steel (BOS). It is used in approximately 65-110 pounds (or 30-59 kg) per tonne of steel. Quicklime neutralises Fe2O3, Al2O3, SiO2, and acidic oxides to form a basic molten slag.

When heated to 4,350 degrees Fahrenheit or 2,400 degrees Celsius, quicklime emits an intense glow. This type of illumination is known as the limelight, and it was widely used in theatrical productions prior to the invention of electric lighting.

Paper: Calcium oxide is used in the chemical recovery of sodium hydroxide from sodium carbonate at kraft pulp mills.

Cement: The primary ingredient used in the manufacturing of cement is calcium oxide. As a widely available and inexpensive alkali. Almost half of total quicklime production is converted to calcium hydroxide before use. Both hydrated- and quick-lime are used to treat drinking water.

Mining: When the compressed lime cartridges exploit the exothermic properties of quicklime, rock can be broken. The rock is drilled with a shot hole as usual, and then a sealed cartridge of quicklime is located and tamped within the shot hole. The cartridge is injected with a small amount of water, resulting in the release of steam, that can break the rock apart when it comes into contact with the larger volume of residual hydrated solid. However, if the rock is particularly hard, this will not work.

Conclusion

Calcium oxide (CaO) is a calcium-containing inorganic material composed primarily of carbonates, oxides, and hydroxides. It has a melting point of 2572 °C (4662 °F) and is a white crystalline solid. It is made by heating limestone, coral, seashells, or chalk, which are mostly composed of CaCO3, in order to remove carbon dioxide. Calcium oxide (in combination with ferrous sulphate) is widely used in wastewater treatment and cement production. The chemical formula for calcium oxide, also known as lime, is CaO. Calcium hydroxide, Ca(OH)2, is the cement in concrete and is known as hydrated lime. Because calcium oxide adheres to bricks and stones, it’s being used as binding material in masonry works. It is also used as a wall coat in whitewashing.