Preparation of Oxygen and Its Properties
Senior 2 · Chemistry
Preparation of Oxygen and Its Properties
Lesson 4 of 4
20 min
During the COVID-19 pandemic, many countries learned how precious medical oxygen is: hospitals that could not get enough of it lost patients who could have been saved. Oxygen also runs much of industry. It helps to turn iron into steel, lets workshops cut and join metal, and launches rockets.
In this lesson you will connect oxygen's properties, especially the way it supports combustion, to its uses in life, medicine and industry, and to the hazards it brings.
Mountaineers on very high peaks, aircraft passengers (the emergency masks), divers and astronauts all carry oxygen supplies.
A fire needs three things: fuel, heat and oxygen. Remove any one and the fire goes out. Fanning a charcoal stove speeds up its supply of oxygen, so it burns hotter. A fire blanket, a lid on a burning pan, sand, or a carbon dioxide extinguisher all work by cutting off the oxygen.
How many moles and what mass of oxygen are needed to burn 26 g of ethyne completely? (C = 12, H = 1, O = 16)
Check the equation: C 4 = 4; H 4 = 4; O 10 = (4 × 2) + 2 = 10.
Warning
Oxygen is not a fuel, but it is a fire hazard
Tip
Memory hook: Breathe, Burn, Build
Oxygen helps us breathe (respiration, hospitals, divers, climbers, astronauts), makes things burn hotter (welding, cutting, rockets) and helps us build (steelmaking). For each use in an exam answer, link it to a property: "it supports combustion" or "it is needed for respiration".
State two medical uses of oxygen.
Solution: Any two of: oxygen therapy for patients with breathing difficulty (pneumonia, asthma, COVID-19); breathing support for premature babies; mixing with anaesthetic gases during surgery; treating carbon monoxide poisoning.
Explain why fanning a charcoal stove makes it burn hotter.
Solution: Fanning brings fresh air, and therefore more oxygen, to the charcoal faster. Combustion speeds up, so more heat is released each second.
Why do welders use pure oxygen rather than air with their fuel gas?
Solution: In pure oxygen the fuel burns much faster and far hotter (over 3 000 °C), because the oxygen is not diluted by nitrogen that would also have to be heated. The flame then melts steel.
How many moles of oxygen are needed to burn 0.50 mol of ethyne completely?
Solution: The ratio C2H2 : O2 is 2 : 5, so 0.50 × 5 ÷ 2 = 1.25 mol of O2.
A pan of cooking oil catches fire. Why should you cover it with a lid or a damp cloth rather than pour water on it?
Solution: Covering it cuts off the oxygen, breaking the fire triangle. Water sinks under the hot oil, boils instantly and throws burning oil out of the pan, spreading the fire.
Summary
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
