Uses of CO2

Major Uses of Carbon Dioxide

Carbon dioxide is not just a waste gas from respiration and combustion. It has many important uses in everyday life, industry, and agriculture. Understanding these uses helps you appreciate why CO₂ is both produced and collected commercially.

1. Fire Extinguishers

Carbon dioxide is one of the most effective substances for putting out fires. Fire needs three things to burn: fuel, heat, and oxygen. CO₂ fire extinguishers work by removing oxygen from the fire.

How it works: When you spray CO₂ from a fire extinguisher, it forms a thick blanket of gas around the burning material. This blanket pushes away oxygen, and without oxygen, the fire cannot continue burning. The gas also cools the burning material slightly, though this is a secondary effect.

Why CO₂ is ideal:

• It does not burn (non-flammable)
• It is denser than air, so it settles over the fire
• It leaves no residue after use (unlike foam or powder)
• It does not conduct electricity, making it safe for electrical fires
• It does not damage equipment or documents

In Nigeria, you see CO₂ fire extinguishers in offices, banks, computer rooms, schools, hospitals, and laboratories. The Lagos State Fire Service and other emergency services use CO₂ extinguishers for specific types of fires, especially electrical fires and fires involving flammable liquids.

Important note: CO₂ extinguishers are not suitable for all fires. Do not use them on metal fires or fires involving reactive chemicals.

2. Carbonated Drinks and Beverages

If you have ever drunk Coca-Cola, Sprite, Fanta, or any soft drink, you have consumed carbon dioxide. The fizz and bubbles you enjoy come from CO₂ dissolved under pressure in the liquid.

How carbonation works: Drink manufacturers force CO₂ gas into the liquid under high pressure. The pressure makes the gas dissolve in the water. When you open the bottle or can, the pressure drops suddenly. The dissolved CO₂ escapes as bubbles, creating the fizzing sound and sensation.

Benefits of CO₂ in drinks:

• Adds a pleasant tingling sensation on your tongue
• Gives drinks a slightly sharp, refreshing taste
• Acts as a preservative by making the drink slightly acidic (CO₂ + H₂O forms weak carbonic acid)
• Prevents growth of harmful bacteria
• Extends shelf life without artificial preservatives

Nigerian Breweries, Coca-Cola Hellenic Bottling Company, and other beverage companies in Lagos, Onitsha, Kano, and Ibadan use thousands of tons of CO₂ yearly for carbonation.

3. Refrigeration and Cooling (Dry Ice)

Solid carbon dioxide is called dry ice. Unlike regular ice made from water, dry ice does not melt into a liquid. It sublimates directly from solid to gas at temperatures below -78°C.

Uses of dry ice:

Food preservation: Ice cream vendors and frozen food suppliers use dry ice to keep products frozen during transport. If you buy ice cream from vendors at Shoprite or Game stores and notice white mist rising from the cooler, that is dry ice sublimating.

Medical transport: Hospitals and medical labs use dry ice to transport vaccines, blood samples, and organs. The Nigerian Centre for Disease Control (NCDC) used dry ice extensively during COVID-19 vaccine distribution, especially for vaccines requiring ultra-cold storage.

Special effects: Stage shows, music videos, and Nollywood productions use dry ice to create fog or mist effects. When dry ice sublimates, it cools the surrounding air and makes water vapor condense, creating a low-lying fog.

Industrial cleaning: Dry ice blasting uses solid CO₂ pellets to clean machinery without water or chemicals. The automotive industry and equipment manufacturers use this method.

4. Baking Industry

Carbon dioxide plays a crucial role in making bread, cakes, and pastries light and fluffy. It helps dough rise in two main ways:

Baking powder: Baking powder contains sodium bicarbonate (NaHCO₃) and an acid (usually cream of tartar). When you add water and heat the mixture, a chemical reaction occurs:

2NaHCO₃ + Heat → Na₂CO₃ + H₂O + CO₂↑

The CO₂ gas produced creates tiny bubbles throughout the dough. These bubbles expand when heated, making the bread or cake rise and become soft.

Yeast fermentation: Bakers also use yeast to produce CO₂ naturally. Yeast feeds on sugar in the dough and produces carbon dioxide and alcohol through fermentation:

C₆H₁₂O₆ (glucose) → 2C₂H₅OH (ethanol) + 2CO₂↑

Local bakeries in Nigerian markets, from Balogun Market in Lagos to Ariaria Market in Aba, depend on baking powder and yeast daily. Without CO₂, bread would be dense and hard instead of soft and spongy.

5. Industrial Chemical Production

Manufacturing companies use CO₂ as a raw material to produce other useful chemicals:

Urea production: Fertilizer factories combine CO₂ with ammonia (NH₃) under high pressure to make urea [CO(NH₂)₂]. Nigerian farmers use urea fertilizer to increase crop yields. The formula is:

2NH₃ + CO₂ → CO(NH₂)₂ + H₂O

Sodium carbonate (washing soda): The Solvay process uses CO₂ to manufacture sodium carbonate, used in glass making, soap production, and water treatment.

Salicylic acid production: Pharmaceutical companies use CO₂ in making aspirin and other pain relievers.

6. Welding and Metal Industries

Metal workers use CO₂ as a shielding gas during welding. When welding, hot metal reacts with oxygen in the air, creating weak, porous joints. Welders spray CO₂ over the welding area to push away oxygen and prevent oxidation.

This technique, called MIG welding (Metal Inert Gas welding), is common in car repair shops, construction sites, and metal fabrication workshops across Nigeria. You see welders at Ladipo Market in Lagos and Ariaria Market in Aba using CO₂ cylinders daily.

7. Enhanced Plant Growth (Agriculture)

Plants need CO₂ for photosynthesis. They take in carbon dioxide and use sunlight to convert it into glucose and oxygen:

6CO₂ + 6H₂O + Sunlight → C₆H₁₂O₆ + 6O₂

Modern greenhouse farmers pump extra CO₂ into greenhouses to speed up plant growth. Higher CO₂ levels (up to 1500 ppm, compared to normal 400 ppm) can increase crop yields by 20-30%.

Agricultural research centers in Nigeria experiment with CO₂ enrichment for growing tomatoes, peppers, cucumbers, and other vegetables in controlled environments.

8. Medical Applications

Doctors and medical professionals use CO₂ in several procedures:

• Laparoscopic surgery: Surgeons inflate the abdomen with CO₂ to create space for operating through small incisions
• Respiratory therapy: CO₂ mixed with oxygen helps stimulate breathing in patients with respiratory problems
• pH balance: Medical labs use CO₂ to maintain proper pH in cell cultures and blood storage

9. Water Treatment

Water treatment plants use CO₂ to adjust pH levels. When water is too alkaline (high pH), adding CO₂ lowers the pH because it forms weak carbonic acid. This process is cheaper and safer than using strong acids like sulfuric acid.

The Lagos Water Corporation and state water boards use CO₂ injection systems to optimize water treatment processes.

Comparison of CO₂ Uses

Why These Uses Are Possible

All these different uses come from CO₂’s unique properties:

• Non-toxic in moderate amounts: Safe to use in food and drinks
• Non-flammable: Cannot catch fire, good for fire fighting
• Denser than air: Settles over fires and can be contained
• Soluble under pressure: Can be dissolved in drinks
• Sublimates: Goes directly from solid to gas, leaving no liquid residue
• Chemically stable: Does not react with most substances at room temperature
• Available cheaply: Produced as byproduct of many industrial processes

Common Exam Mistakes

WAEC examiners report these common errors when students answer questions about uses of CO₂:

1. Vague answers: Writing “used in industry” without specifying which industry or what process
2. Confusing dry ice with regular ice: Saying dry ice melts instead of sublimates
3. Not explaining how it works: Stating “used in fire extinguishers” without explaining that it cuts off oxygen supply
4. Wrong chemical formulas: Writing CO instead of CO₂, or confusing urea’s formula
5. Incomplete statements: Mentioning “used in drinks” without saying carbonated or soft drinks
6. Mixing up properties and uses: Listing properties like “colorless” instead of actual uses
7. Forgetting Nigerian context: Using only foreign examples instead of relating to local applications

Practice Questions

Multiple Choice Questions

1. Which of the following is NOT a use of carbon dioxide?

a) Fire extinguisher
b) Carbonated drinks
c) Fuel for vehicles ✓
d) Refrigeration

2. Solid carbon dioxide is called:

a) Ice
b) Dry ice ✓
c) Frozen CO₂
d) Carbon ice

3. CO₂ is used in fire extinguishers because it:

a) Burns the fuel completely
b) Cuts off the oxygen supply ✓
c) Reduces the heat
d) Changes the fuel to ash

4. In baking powder, CO₂ is released from:

a) Carbon monoxide
b) Calcium carbonate
c) Sodium bicarbonate ✓
d) Magnesium carbonate

Essay/Theory Questions

1. State five uses of carbon dioxide and explain two of them in detail. (8 marks)

Answer should include: (i) list five uses – fire extinguisher, carbonated drinks, dry ice, baking, industrial chemicals (5 marks), (ii) detailed explanation of any two uses with how CO₂ works in each application (3 marks total – 1.5 marks per explanation)

2. Explain how carbon dioxide is used in fire extinguishers and state why it is effective. (5 marks)

Answer should cover: (i) CO₂ is sprayed on fire (1 mark), (ii) it forms a blanket around burning material (1 mark), (iii) it displaces/cuts off oxygen (1 mark), (iv) fire stops because oxygen is removed (1 mark), (v) CO₂ is non-flammable and denser than air (1 mark)

3. Describe how carbon dioxide is used in the beverage industry. What are the advantages of using CO₂ in soft drinks? (6 marks)

Answer should include: (i) CO₂ is dissolved in drinks under pressure (1 mark), (ii) creates fizz/bubbles when opened (1 mark), (iii) advantages: adds pleasant taste (1 mark), acts as preservative (1 mark), prevents bacterial growth (1 mark), extends shelf life (1 mark)

4. What is dry ice? State three uses of dry ice and explain why it is preferred over ordinary ice in some applications. (7 marks)

Answer: (i) dry ice is solid CO₂ (1 mark), (ii) three uses: refrigeration, food preservation, medical transport, special effects (3 marks), (iii) advantages over ordinary ice: colder temperature -78°C (1 mark), sublimates without leaving liquid (1 mark), does not wet materials (1 mark)

Memory Aids

To Remember Major Uses (FARBD):

• F – Fire extinguisher
• A – Agriculture (plant growth)
• R – Refrigeration (dry ice)
• B – Baking powder
• D – Drinks (carbonated)

Why CO₂ Stops Fire:

“Fire Needs Oxygen, CO₂ Cuts Supply” – Remember: CO₂ blocks oxygen, fire dies

Dry Ice Properties:

“Solid to Gas, No Liquid Mess” – Dry ice sublimates, never melts

Related Topics

• Test for Carbon Dioxide
• Laboratory Preparation of CO₂
• Properties of Carbon Dioxide
• Carbon Cycle in Nature
• Greenhouse Gases and Climate Change