What is Carbon Dioxide (CO2)? Properties, Production Methods, and Applications

Definition of Carbon Dioxide:

Carbon dioxide, also known as carbonic oxide (and by various other names such as carbonic acid gas, carbonic anhydride, or carbonic gas), is a gaseous chemical compound present in the Earth’s atmosphere under normal conditions. Carbon dioxide consists of one carbon atom and two oxygen atoms. In its solid form, carbon dioxide is also referred to as dry ice.

What is carbon dioxide (CO2)?

• Chemical Formula: CO2
• Molar Mass: 44

Molecular Structure:

In the CO2 molecule, each carbon atom contributes 4 electrons to bonding. In each C-O bond, carbon donates 2 electrons while oxygen lacks 2 electrons. Therefore, each C-O bond shares a total of 4 electrons, forming a double bond (consisting of a stable π bond and a σ bond). This is a polar covalent bond, but due to its linear structure, CO2 is a nonpolar molecule.

Carbon dioxide (CO2) is obtained from various sources, including:

• Gas emitted from volcanoes, combustion products of organic compounds, and the respiratory activities of living organisms.
• Additionally, CO2 is produced through the fermentation of certain microorganisms and cellular respiration. Plants absorb CO2 during photosynthesis and utilize carbon and oxygen to produce carbohydrates. Plants also release oxygen back into the atmosphere, which is used by heterotrophic organisms during respiration, forming a cycle.
• It appears in the Earth’s atmosphere at low concentrations and acts as a greenhouse gas, becoming a major component in the carbon cycle.

Physical Properties of Carbon Dioxide

Being present in our surroundings, what notable physical properties does carbon dioxide possess?

What physical properties does carbon dioxide (CO2) have?

• Color, Odor: Carbon dioxide (CO2) is a colorless and odorless gas, heavier than air with a density of (CO2/air) = 44/29. At a temperature of 25 °C, CO2 is approximately 1.5 times denser than air.
• Gas Dissolved in Water: Inhaling high concentrations of carbon dioxide can cause a sour taste in the mouth and a tingling sensation in the nose and throat. These effects occur due to the gas dissolving in water, forming a weak solution of carbonic acid.
• Decomposition: Carbon dioxide can be decomposed at high temperatures of 2000 oC, resulting in the formation of CO and O2. CO2 is formed as a solid when rapidly cooled (below -78 °C). In this state, it condenses into white crystalline structures known as dry ice. Dry ice sublimates directly into a gaseous state without melting into liquid CO2 under normal pressure.
• The CO2 molecule (O = C = O) contains two double bonds and has a linear shape. It is nonpolar. As it is a fully oxidized compound, it does not support combustion.
• Boiling Point: -78 oC (-108 oF; 195K)
• Specific Gravity: CO2 has a density of 1.98 kg/m^3 (at 25 oC)
• Melting Point: -57 oC (-71 oF; 216K) (under pressure)

Chemical Properties of Carbon Dioxide

Carbon dioxide (CO2) exhibits typical chemical properties of an acidic oxide.

Chemical properties of carbon dioxide.

Carbon dioxide dissolves in water to form carbonic acid (a very weak diacid)

To demonstrate this, an experiment is conducted by placing a piece of litmus paper into a test tube containing water and then bubbling CO2 gas into the test tube. Upon heating the resulting solution, the observation is made that the litmus paper initially turns red and then violet after heating.

This reaction leads to the conclusion that CO2 reacts with water to form an acidic solution, causing the litmus paper to turn red. H2CO3 is unstable and easily decomposes into CO2 and H2O, which turns the litmus paper from red to violet upon heating.

Equation: CO2 (g) + H2O (l) ↔ H2CO3 (aq)

Carbon dioxide reacts with a basic solution

The reaction with a basic solution is one of the reactions that demonstrate the important chemical properties of carbon dioxide. CO2 reacts with a basic solution to form a salt and water according to the following equation:

CO2 (g) + 2NaOH (aq) → Na2CO3 (aq) + H2O (l)

1 mol 2 mol

CO2 (g) + NaOH (aq) → NaHCO3 (aq)

1 mol 1 mol

The reaction can produce a neutral salt, an acid salt, or a mixture of two salts depending on the mole ratio of CO2 to NaOH.

Carbon dioxide reacts with basic oxides

CO2 exhibits the characteristic chemical properties of an acidic oxide as it reacts with basic oxides to form salts.

Equation: CO2 (g) + CaO (s) → CaCO3 (s)

Carbon dioxide production

How is carbon dioxide produced? In this section, we will explore two common methods of carbon dioxide production in laboratories and industries.

Learn how to prepare CO2.

Production of carbon dioxide in the laboratory

In the laboratory, CO2 is often produced from CaCO3 and HCl solution. However, this method yields a product that contains some hydrogen chloride gas and water vapor.

Production equation: CaCO3 + 2HCl → CaCl2 + CO2 + H2O

To obtain pure CO2 gas, the gas mixture is passed through a flask containing excess NaHCO3 solution, which retains the hydrogen chloride gas. The remaining mixture is then passed through a flask containing concentrated H2SO4 or P2O5, where water vapor is absorbed, resulting in the collection of pure CO2.

Production of carbon dioxide in the industry

In industries, CO2 is produced by the complete combustion of coal in air, according to the equation: C + O2 → CO2

Alternatively, limestone can be thermally decomposed to generate carbon dioxide, as shown by the equation:

CaCO3 → CaO + CO2 (at 1000 °C)

Furthermore, carbon dioxide can be obtained from human or animal respiration, the fermentation process in brewing and alcohol production, and the combustion of fuels:

• Human or animal respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O
• Fermentation process in brewing: C6H12O6 → 2CO2 + 2C2H5OH
• Combustion of fuels: CxHy + (x+y/4)O2 → XCO2 + (y/2)H2O

Applications of carbon dioxide

With its physical properties and chemical characteristics, carbon dioxide is a widely applied chemical compound in various aspects of human life and important industries such as industrial, medical, and food technology.

Carbon dioxide is a compound commonly used in industry.

Applications of CO2 in the industry

Carbon dioxide is an important compound with widespread industrial applications. So, what are these applications?

• Used as a low-cost, non-flammable compressed gas. Therefore, it is used in life jackets, airgun cartridges, bicycle pumps, and soda siphons. Carbonic acid-filled steel cylinders are also sold to provide compressed air for airguns, bicycle tire pumps, and soda water. The rapid evaporation of liquid CO2 is also used for explosion purposes in coal mines.
• In many types of fire extinguishers, liquid CO2 (carbon dioxide) is used to extinguish fires caused by burning or electrical sparks.
• Despite its reactivity with most metals, CO2 is still applied as a shielding gas in welding technology. However, this welding process may decrease in quality due to the formation of carbonic acid and it is more brittle compared to inert gas environments such as argon or helium.

Applications of CO2 in medicine

Besides the industrial sector, CO2 also plays an important role in the field of medicine, specifically:

Carbon dioxide plays an important role when added to pure oxygen (5%) to help patients breathe.

• Serves as a good solvent for many organic compounds and is used as a less toxic alternative to traditional solvents such as organic chlorides. It is also used to extract caffeine from coffee.
• Carbon dioxide (CO2) plays a crucial role when added to pure oxygen (5%) for respiratory support in patients to stabilize and balance oxygen/carbon dioxide levels in the blood.
• As carbon dioxide is the primary raw material for photosynthesis, it is pumped into greenhouses to stimulate plant growth. Additionally, CO2 is applied to eradicate various pests at high concentrations.

Applications of CO2 in daily life

In daily life, carbon dioxide in the form of dry ice is used to create a fog effect, commonly seen in events such as weddings, game shows, and more.

Note: When using dry ice, gloves should be worn to avoid cold burns, and it should not be stored in sealed containers as the pressure caused by dry ice can cause the container to explode.

Applications of CO2 in food technology

In the field of food technology, carbon dioxide (CO2) also plays a crucial role, notably:

In the food industry, CO2 plays a very important role.

• In food technology, carbon dioxide is compressed and cooled to form dry ice, which is used as an important refrigerant for transportation and preservation of frozen products, ice creams, etc.
• In the beverage industry, CO2 is utilized to carbonate various carbonated drinks such as Coca-Cola, Pepsi, 7UP, providing them with fizziness.
• Due to its characteristic “volatility,” CO2 is applied in the preservation of perishable food items.
• Carbon dioxide is also employed in food extraction processes, particularly through the use of supercritical carbon dioxide, which helps remove oils and fats and is utilized in extracting colors and flavors in food products.

Is CO2 poisonous, and precautions when using it

According to statistics, humans have been releasing an increasing amount of CO2 into the atmosphere. The primary source of this carbon dioxide is the combustion of coal and natural gas in power plants, fertilizer production, cement manufacturing, and other industrial processes.

CO2 is not inherently toxic, but if present in high concentrations, it can deplete oxygen in the air, causing direct harm to the environment and human health.

Is CO2 toxic?

Impact on the environment

The increasing concentration of carbon dioxide in the environment exacerbates the greenhouse effect. This phenomenon leads to global warming, directly impacting and threatening human and animal life on Earth.

Rapid increases in carbon dioxide levels can hinder protein synthesis. When insects consume plants with insufficient protein, their mortality rates increase, causing harm to ecosystems.

Impact on human health

High concentrations of carbon dioxide in the air can reduce oxygen levels, resulting in health hazards such as fatigue, breathlessness, nervous stimulation, increased heart rate, and various other disorders.

When carbon dioxide levels are excessively high in the air, although not a toxic gas, it severely affects human health and can even lead to death.

Furthermore, direct contact of the skin with solid carbon dioxide (dry ice) can cause frostbite, resulting in numbness and stiffness of the affected body parts.

Handling carbon dioxide poisoning

In addition to chest discomfort, initial symptoms of carbon dioxide poisoning may include headaches, fatigue, dizziness, drowsiness, or nausea. Sudden chest pain may occur in individuals with a history of angina. Prolonged exposure can worsen symptoms, accompanied by vomiting, fainting, loss of consciousness, and muscle weakness.

How to deal with CO2 poisoning?

The symptoms of CO2 poisoning can vary depending on each case. CO2 poisoning can occur earlier in certain individuals, such as young children, the elderly, those with lung or heart disease, people at high altitudes, and smokers.

How can CO2 poisoning be treated when detected?

Since CO2 is heavier than air, it is advisable to move the affected person to higher ground in cases of CO2 poisoning. (Note: Only do this when the environment is not hazardous to the rescuer, and only trained and professionally qualified rescuers should administer emergency oxygen to CO2-poisoned individuals.)

If there are life-threatening factors involved, it is necessary to call for emergency medical assistance for timely help.

CO2 storage considerations

To ensure safety when using CO2 gas, it is important to pay attention to its storage and transportation as a chemical compound.

Precautions when using CO2 gas

CO2 gas in storage containers usually exists in liquid form and needs to be heated to convert it into gas. Therefore, it is important to attach a heat drying device to CO2 gas regulating valves to prevent blockage due to freezing.

Only use a respirator mask with a valve when the user has received training on proper usage.

It is essential to understand the benefits of installing gas detection equipment to prevent and handle situations promptly.

Considerations for storing and transporting CO2 gas

When storing carbon dioxide, CO2 should be contained in pressure-resistant and thermally insulated steel containers or pressure-resistant sealed cylinders.

When filling liquid CO2, the filling should not exceed 0.625 kg/liter for containers and 0.9 kg/liter for cylinders. Take precautions to avoid strong impacts on cylinders or containers, keep CO2 away from heat sources, and if long-term storage in containers is necessary, ensure a separate refrigeration system.

When transporting liquid CO2 cylinders, they should be placed horizontally with the valves of all cylinders facing the same direction, and padding should be used between cylinders. The transporting vehicle must have a protective cover.

With important information about what carbon dioxide is, its properties, production methods, and applications of this compound, I hope the article has provided you with valuable knowledge. Additionally, you can refer to many other helpful resources for studying other chemistry topics on Monkey’s website. Don’t forget to share if you find the article useful!