Calcium Oxide

Calcium oxide is a white, caustic alkaline which is solid at room temperature. Calcium Oxide is known as quicklime is a material which is a commonly used material. Calcium Oxide reactivity with water, along with its other chemical properties, makes it a very important chemical in various fields.

In this article we will learn in detail about calcium oxide, its properties, applications and other details in detail.

What is Calcium Oxide?

Calcium oxide is a white crystalline substance (an inorganic compound) having the chemical formula CaO. Its common name is quicklime. Calcium oxide is composed of one calcium (Ca) atom and one oxygen (O) atom, with a chemical formula of CaO.

Calcium oxide has a high melting point of approximately 2,572 degrees Celsius (4,662 degrees Fahrenheit). It has a high density so it is a heavy substance.

Calcium Oxide Common Name

Common Name of Calcium Oxide is Quicklime.

Calcium Oxide Chemical Formula

Chemical Formula of calcium oxide is CaO.

Calcium Oxide Molecular Weight

Molecular weight of calcium oxide is approximately 56.08 amu.

The Molecular Weight of Calcium Oxide can be obtained as

• Atomic weight of calcium is approximately 40.08 grams per mole (g/mol).
• Atomic weight of oxygen is approximately 16.00 g/mol.

Molecular Weight of CaO = Atomic Weight of Ca + Atomic Weight of O

⇒ Molecular Weight of CaO = 40.08 g/mol + 16.00 g/mol

⇒ Molecular Weight of CaO = 56.08 g/mol

Calcium Oxide Melting Point

Calcium oxide has a very high melting point.

Calcium Oxide Melting Point is approximately 2572℃ (4662℉)

This high melting point is characteristic of many ionic compounds, and it reflects the strong electrostatic forces of attraction between the positively charged calcium ions and the negatively charged oxide ions in the crystal lattice of the solid CaO.

Structure of CaO Molecules

Calcium oxide molecules contain one calcium cation (which holds a charge of +2) and one oxygen anion (which holds a charge of -2).

Lewis Dot Structure of Calcium Oxide

Lewis dot structure of calcium oxide (CaO) is drawn by considering the valence electrons of each element and their bonding.

• Calcium (Ca) is in Group 2 of the periodic table, so it has 2 valence electrons.
• Oxygen (O) is in Group 16 of the periodic table, so it has 6 valence electrons.

In this structure, the two oxygen atoms are bonded to the calcium atom via double bonds, and each oxygen atom has a full octet of electrons, while calcium has lost two electrons to achieve a stable electron configuration.

Lime Water Formula

The formula for lime water is Ca(OH)₂ and the chemical name for lime water is calcium hydroxide. When water is added to lime calcium hydroxide Ca(OH)₂ is formed according to the following reaction.

CaO + H₂O → Ca(OH)₂

Preparation of Calcium Oxide

Calcium oxide is prepared by the process called calcination. Calcination involves heating calcium carbonate (CaCO₃) to a high temperature, causing it to decompose and release carbon dioxide (CO₂), leaving behind calcium oxide (CaO) as the final product.

CaCO₃(g) → CaO(s) + CO(g)

Sources of Calcium Carbonate: It can be obtained naturally i.e. occurring in minerals such as limestone, chalk, or marble.

Physical Properties of Calcium Oxide

The physical properties of calcium oxide are essential to understand its behavior and applications in various fields.

• Appearance: CaO is a white, odorless, and crystalline solid at room temperature. It is typically found in the form of small white or grayish-white crystals or a fine powder.
• Melting Point: CaO has a high melting point of approximately 2,572 degrees Celsius (4,662 degrees Fahrenheit).
• Hygroscopic: This property makes it essential to store quicklime in a dry environment and in airtight containers to prevent its reaction with water.
• Crystal Structure: The crystal structure of calcium oxide is often described as being cubic or face-centered cubic (FCC).
• High Electrical Conductivity: CaO, in its molten state or in the presence of water, exhibits high electrical conductivity.

Properties	Value
Molar Mass	56.0774 g/mol
Boiling Point	2,850 °C
Melting Point	2,572 °C
Density	3.34 g/cm³

Chemical Properties of Calcium Oxide

Calcium oxide exhibits wide range of chemical properties and some of its important chemical properties includes:

Reactivity with Water

Calcium oxide is highly reactive with water, and when it comes in contact with water, it undergoes a vigorous exothermic reaction. This reaction results in the formation of calcium hydroxide [Ca(OH)₂] and the release of a significant amount of heat. The equation for this reaction is

CaO + H₂O → Ca(OH)₂

• Carbonation: Calcium oxide can absorb carbon dioxide from the atmosphere, converting back into calcium carbonate (CaCO₃).
• Desiccant Properties: Calcium oxide is a strong desiccant, meaning it has a strong affinity for moisture. It can be used to remove water from gases and liquids, making it valuable in drying applications, including the removal of moisture from industrial processes.
• Reactivity with Carbon: Calcium oxide when heated in the presence of carbon, reduces carbon dioxide to produce carbon monoxide. T
• Electrolysis: In molten form or in the presence of water, calcium oxide exhibits electrical conductivity. This property can be used in processes like the electrolysis of metals.
• Strong Alkalinity: Calcium oxide is a strong alkaline compound which has the ability to increase the pH of solutions, making it useful in applications where alkalinity is required.
• Reduction Reactions: Calcium oxide can also behave as a reducing agent, participating in various reduction reactions.

Calcium Oxide Chemical Reactions

Calcium oxide undergoes various chemical reactions due to its high reactivity but some of the most common reactions of calcium oxide are:

Formation of Calcium Hypochlorite:

When calcium oxide reacts with chlorine gas (Cl₂), it can form calcium hypochlorite [Ca(ClO)₂], a compound often used in water treatment and as a bleaching agent.

CaO + Cl₂ → Ca(ClO)₂

Uses of Calcium Oxide

Calcium oxide is a versatile compound having many applications across various industries. Some of its common uses are:

• Chemical Industry: It is used as a precursor in the production of various chemicals, such as calcium stearate, used in the manufacture of plastics and soaps.
• Metallurgy: In the metallurgical industry, calcium oxide is used to remove impurities and slag during the extraction of metals from ores.
• Water Treatment: Calcium oxide can be used for water softening by removing excess calcium and magnesium ions that causes water hardness.
• Construction Industry: Calcium oxide is a fundamental ingredient in the production of mortar and plaster.
• Environmental Impact: Calcium oxide plays a crucial role in resolving environmental issues like improvement in air quality, improvement in water quality , agricultural sustainability, etc.
• Metallurgy: In the extraction of metals from ores, calcium oxide is used to remove impurities.

Safety Tips

• The reaction between quicklime and water is vigorous.
• Quicklime can cause irritation, especially when inhaled or if it comes in contact with wet skin or eyes.
• Some of the effects of inhalation include sneezing, coughing, or laboured breathing.
• Also, it can result in abdominal pain, nausea burns with perforation of the nasal septum, and vomiting.
• When quicklime reacts with water it release heat to combustible materials.

Sample Questions on Calcium Oxide

Question 1: What is the Chemical Formula of Oxide?

Answer:

Chemical Formula of Calcium Oxide is CaO.

Question 2: How Calcium oxide is prepared?

Answer:

Calcium oxide is prepared by the process called calcination which involves heating the calcium carbonate (CaCO₃) at high temperature, causing it to decompose and release carbon dioxide (CO2), leaving behind calcium oxide (CaO).

CaCO₃(g)→CaO(s) + CO(g)

Question 3: What is the primary use of calcium oxide in industry?

Answer:

The primary use of calcium oxide in the industry is in the production of cement. Calcium oxide plays an important in the manufacturing of Portland cement, which is the most widely used type of cement in construction and building applications.

Question 4: What is the state of calcium oxide at room temperature?

Answer:

Calcium oxide is a solid at room temperature.

Question 5: What are the physical properties of calcium oxide?

Answer:

Physical properties of calcium oxide are:

• Physical State: White crystalline solid or powder at room temperature.
• Melting Point: High melting point at approximately 2,572 degrees Celsius (4,662 degrees Fahrenheit).
• Boiling Point: No distinct boiling point; undergoes thermal decomposition at high temperatures.
• Density: Relatively dense with a density of about 3.34 grams per cubic centimeter.
• Solubility: Sparingly soluble in water, forming calcium hydroxide when in contact with water.
• Odor and Taste: Lacks a characteristic odor or taste.

Calcium Oxide Frequently Asked Questions

What is Calcium Oxide?

Calcium oxide is a white crystalline substance(an inorganic compound) having chemical formula CaO and is also known as quicklime.

What are the sources of calcium carbonate?

It is basically found in natural minerals such as limestone, chalk, or marble.

How Calcium Oxide can be used to form Calcium Hydroxide?

Calcium oxide reacts vigorously with water to produce calcium hydroxide [Ca(OH)₂] and significant amount of heat is released.

CaO + H₂O → Ca(OH)₂ + heat

How can Calcium Oxide improves Air and Water Quality?

Calcium Oxide captures sulfur dioxide which helps to reduce acid rain formation and air pollution, contributing to improved air quality and reduced environmental harm and it also aids in improving water quality by reducing hardness and the presence of heavy metals, making it safer for consumption and industrial use.

Why Calcium Oxide is used in Alkaline Battery Production?

Calcium oxide is used as an important component in alkaline batteries, where it helps to regulate the pH of the battery electrolyte.

Is Calcium Oxide Soluble in Water?

Calcium oxide is only sparingly soluble in water. When calcium oxide is added to water, it undergoes a vigorous exothermic reaction to produce calcium hydroxide [Ca(OH)₂].

Is Calcium Oxide Ionic or Covalent?

Calcium oxide is an ionic compound. It is formed by the combination of a metal (calcium) and a non-metal (oxygen).

What is the Reaction of Water with Calcium oxide?

This reaction results in the formation of calcium hydroxide [Ca(OH)₂] and the release of a significant amount of heat. The equation for this reaction is CaO + H₂O → Ca(OH)₂