Uses Of Oxygen

Detailed Explanation of Oxygen Uses

Oxygen is the third most abundant element in the universe and makes up about 21% of Earth’s atmosphere. Its unique ability to support combustion and sustain life makes it valuable for many purposes.

1. Respiration and Life Support

All living things need oxygen to survive. When you breathe in, oxygen enters your lungs and moves into your blood. Your cells use this oxygen to break down food and release energy through a process called cellular respiration. Without oxygen for more than a few minutes, brain cells start dying.

Plants also need oxygen for respiration, though they produce it during photosynthesis in daylight. At night, plants use oxygen just like animals do. Fish get oxygen dissolved in water through their gills.

2. Medical Uses

Hospitals use oxygen to treat patients who cannot get enough oxygen on their own. Doctors give medical oxygen to people with:

• Pneumonia and severe cough
• Heart problems that affect breathing
• Asthma attacks
• Carbon monoxide poisoning
• Premature babies with underdeveloped lungs
• Surgical patients under anesthesia

Ambulances in Lagos, Port Harcourt, and other Nigerian cities carry oxygen cylinders for emergency treatment. Medical oxygen must be very pure (at least 99.5%) to avoid harming patients.

3. Industrial Welding and Cutting

Oxy-acetylene welding uses oxygen mixed with acetylene gas (also called ethyne) to create extremely hot flames reaching 3,500°C. This high temperature can melt steel and other metals for joining or cutting.

Welders working on bridges, pipelines, and construction sites across Nigeria use this method. The reaction is:

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O + Heat

The intense heat from burning acetylene in pure oxygen makes it perfect for metalwork that regular flames cannot handle.

4. Steel Industry

Steel mills like Ajaokuta Steel Company use oxygen to convert pig iron into steel. Pig iron from blast furnaces contains too much carbon (about 4%) and impurities like sulfur and phosphorus.

Workers blow pure oxygen through molten pig iron in a process called basic oxygen steelmaking. The oxygen reacts with carbon and other impurities, removing them as gases or slag. This produces steel with only 0.1-1.5% carbon, making it stronger and more useful.

The reactions include:

• 2C + O₂ → 2CO (carbon removed as gas)
• S + O₂ → SO₂ (sulfur removed as gas)
• 4P + 5O₂ → 2P₂O₅ (phosphorus forms slag)

5. Rocket Propellants

Space rockets need huge amounts of energy to escape Earth’s gravity. Liquid oxygen (LOX) stored at -183°C is mixed with rocket fuel like kerosene or liquid hydrogen.

When the fuel burns in oxygen, it releases enormous energy that pushes the rocket upward. NASA’s Space Shuttle used 1.4 million liters of liquid oxygen per launch. The reaction for hydrogen fuel is:

2H₂ + O₂ → 2H₂O + Energy

This reaction releases more energy per kilogram than any other chemical fuel combination.

6. Chemical Manufacturing

Many important chemicals need oxygen for production:

• Sulfuric acid (H₂SO₄): Used in car batteries and fertilizer production. Made by oxidizing sulfur dioxide with oxygen
• Nitric acid (HNO₃): Used in making explosives and fertilizers. Produced by oxidizing ammonia with oxygen
• Ethylene oxide: Used for making plastics and antifreeze
• Titanium dioxide: White pigment in paints sold at markets across Nigeria

Nigeria’s chemical industries in Port Harcourt, Kaduna, and Lagos depend on oxygen for these manufacturing processes.

7. Water Treatment

Water treatment plants use oxygen to purify drinking water. They bubble oxygen through water containing organic waste. Bacteria use this oxygen to break down harmful substances, making the water safe to drink.

This process (called activated sludge treatment) cleans water in Lagos, Abuja, and other cities before it reaches your tap. The same method treats sewage to protect rivers and lagoons from pollution.

8. Combustion and Engines

Car engines need oxygen from air to burn petrol or diesel. The fuel mixes with air in the engine cylinder and burns, pushing the piston down to turn the wheels.

For petrol: 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O + Energy

Without enough oxygen, fuel burns incompletely, producing dangerous carbon monoxide (CO) instead of carbon dioxide. This is why cars should never run in closed garages.

9. Other Uses

• Scuba diving: Divers breathe compressed air (containing oxygen) from tanks underwater
• Mountain climbing: Climbers carry oxygen cylinders for high altitudes where air is thin
• Glass manufacturing: Oxygen-enriched flames melt sand at high temperatures
• Paper bleaching: Paper mills use oxygen to whiten paper pulp
• Fish farming: Oxygen pumps keep fish alive in crowded ponds

Comparison Table: Medical vs Industrial Oxygen

Warning: Never use industrial oxygen for medical purposes. The impurities can harm lungs and cause serious health problems.

Common Exam Mistakes

WAEC and NECO examiners report these frequent errors:

1. Confusing “uses” with “properties”: Students write “oxygen supports combustion” (a property) instead of “oxygen is used in welding” (a use). A use shows how we apply oxygen’s properties.
2. Vague answers: Writing “oxygen is used in hospitals” without explaining why or how. Always give specific conditions treated (pneumonia, asthma attacks).
3. Wrong chemical formulas: Writing C₂H₂ as C₂H₆ or showing incorrect balanced equations for combustion. Check your formulas carefully.
4. Mixing up gases: Stating nitrogen is used for welding instead of oxygen, or claiming oxygen makes up 78% of air (that’s nitrogen).
5. Not reading the question: When asked to “state five uses,” students explain one use in five sentences instead of listing five different uses. “State” means list briefly; “explain” means give details.
6. Poor English expression: Writing “oxygen is for breath” instead of “oxygen is used for respiration” or “breathing.”

Practice Questions

Multiple Choice Questions

1. Which process uses oxygen to remove impurities from pig iron?
a) Fractional distillation
b) Basic oxygen steelmaking ✓
c) Electrolysis
d) Haber process

2. The oxy-acetylene flame used in welding can reach temperatures of approximately:
a) 500°C
b) 1,200°C
c) 3,500°C ✓
d) 10,000°C

3. Medical oxygen must have a minimum purity of:
a) 85%
b) 90%
c) 95%
d) 99.5% ✓

4. Which chemical uses oxygen in its production and is found in car batteries?
a) Hydrochloric acid
b) Sulfuric acid ✓
c) Acetic acid
d) Citric acid

Essay Questions

1. (a) State FIVE uses of oxygen in everyday life and industry. (5 marks)
(b) Explain how oxygen is used in the steel manufacturing process. (5 marks)

Examiner’s Tip: For part (a), simply list five uses briefly. For part (b), explain the process of removing impurities from pig iron using oxygen, and write at least one chemical equation.

2. (a) Distinguish between medical oxygen and industrial oxygen. (4 marks)
(b) Explain why industrial oxygen should not be used for medical purposes. (3 marks)
(c) Describe TWO ways oxygen supports life. (3 marks)

Examiner’s Tip: “Distinguish” means show clear differences. Use a table or comparison format. For 4 marks, give at least 3-4 differences.

3. A student wrote: “Oxygen is used in combustion.” The teacher said this answer is incomplete.
(a) Give THREE specific examples of how oxygen’s combustion property is used practically. (6 marks)
(b) Write a balanced equation for the complete combustion of octane (C₈H₁₈) in car engines. (4 marks)

Examiner’s Tip: Each example should name a specific application (e.g., car engines, cooking gas, welding) and briefly explain it. That’s 2 marks per example.

Memory Aids

Mnemonic for Major Uses – “WOMEN CRY”

• Welding (oxy-acetylene flame)
• Oxidizer in rockets
• Medical treatment
• Engines and combustion
• Nutrient for cells (respiration)
• Chemical manufacturing
• Refining steel (removing impurities)
• You need it to live!

Remember the combustion equation pattern:
Hydrocarbon + Oxygen → Carbon dioxide + Water + Energy
(This works for complete combustion of any fuel)

Related Topics

• Chemical Properties of Oxygen – Learn how oxygen reacts with other elements
• Physical Properties of Oxygen – Understand oxygen’s characteristics and behavior
• Test for Oxygen – Laboratory methods to identify oxygen gas
• Nitrogen – Compare with oxygen’s occurrence and uses
• Air Pollution – See effects when oxygen combines with pollutants during combustion