Oxygen

Oxygen, commonly known as O2, is the most crucial element that sustains life on earth. It is a colourless, tasteless, odourless gas, is highly reactive and forms oxides when it comes in contact with other elements. Its chemical symbol is ‘O’ and has 8 as its atomic number. It is present as a diatomic molecule (O2). 

O2, by volume, forms 21 per cent of the atmosphere and by weight, it forms 50 per cent of the earth’s crust. It has numerous industrial and metallurgical purposes. It is also used in rocket engines, wastewater treatment processes and scuba divers.

History of Oxygen

Oxygen was discovered by Joseph Priestley, an English chemist, in 1774. However, in 1772, Carl Wilhelm Scheele was the first to obtain it by heating compounds like Potassium Nitrate and Mercuric Oxide but published his findings three years later than Priestley. Later, a French chemist, Antoine-Laurent Lavoisier, demonstrated its role in respiration as well as in combustion.

Occurrence on earth

Oxygen is one of the most abundant elements in the earth’s biosphere. It makes up 21% of the earth’s atmosphere, 89% of seawater, and more than 50 per cent of the earth’s crust. It combines with other elements to form oxides of metals and non-metals. Earth is the only planet having such a high concentration of O2, which leads to the formation of O2 cycles.

Properties of Oxygen

• Oxygen is a pale blue liquid below -183 degrees Celsius, and solid at -218 degrees Celsius. 

• It is 1.1 times heavier than that air. 

• During photosynthesis, green plants use carbon dioxide to produce O2, which is needed by all living organisms to respire.

• O2 has three naturally existing isotopes, although artificial isotopes have also been made now.

Allotropes of O2 

Oxygen exists in two forms, diatomic (O2) and triatomic (O3 or Ozone). The formation of ozone is endothermic (energy-requiring), while its conversion to O2 can be done by transition metals or with their oxides. 

Pure O2 is converted to ozone by electrical discharges too in the upper atmosphere. Ozone is light blue in colour, is 1.6 times heavier than air, having a boiling point of -112 degrees Celsius. It finds use as a chemical agent, as a commercial disinfectant in wastewater treatments, and for bleaching textiles. 

Another allotrope of Oxygen was discovered in 2001 called the tetra-oxygen molecule, which was a much more powerful oxidising agent than O2 or O3, making it suitable for use in rocket fuels. Another phase of solid O2 was found in 1998 which when subjected to very high pressures and low temperatures, behaves like a superconductor.

How is Oxygen produced?

O2 is produced from the fractional distillation of liquid air. Here are some common methods of production of Oxygen:

• By the thermal decomposition of potassium nitrate and potassium chlorate with the help of a catalyst:

2KClO3 → 2KCL +O2

2KNO3 → 2KNO2 + O2

• Through the electrolysis of water:

2H2O → 2H2 + O2

• By the thermal decomposition of heavy metallic oxides:

2HgO → 2Hg +O2

2Ag2O → 4Ag +O2

• By the thermal decomposition of metal peroxides or hydrogen peroxide:

2H2O2 → 2H2O +O2

2Ba + O2 → 2BaO2

2BaO2 → 2Ba +O2

Commercial and industrial applications of Oxygen 

Here are some of the most common commercial and industrial applications of Oxygen:

• Sewage treatment plants use O2 for treating liquid effluents. 

• Pure O2 is used in rocket fuels, submarines, scuba gears and diving bells. 

• It is also used in the steel industry in blowing high carbon steel, which refers to the process of volatilizing carbon and other non-metallic impurities with the help of O2 in a much more efficient way. 

• It is also used commercially in the manufacture of acetylene, methanol and ethylene oxides. 

• Medically, it is used in general anaesthesia, in paediatric incubators and inhalators. 

• Oxygen also finds application in several industries that use kilns.

Conclusion

O2 is the major element that is crucial for the survival of all life forms, and this guide will act as an introduction to Oxygen for you. Oxygen is present in animal shells, teeth and bones. It is also present in the major classes of organic compounds like proteins, carbohydrates, fats and nucleic acids. Most of the earth’s free O2 is replenished by photosynthesis. Oxygen along with its various forms finds usage across multiple industries. Its allotrope, ozone, absorbs the harmful ultraviolet rays of the sun in the upper atmosphere (stratosphere).