Oxygen is a chemical element that is essential for life, and it is found in many compounds, including water and carbon dioxide. There are several methods used to prepare oxygen, depending on the source and the desired purity of the oxygen.
Fractional Distillation of Liquid Air: Oxygen is one of the components of air, which is a mixture of gases. By fractional distillation of liquid air, Oxygen can be obtained by cooling the air to very low temperatures until it liquefies, and then distilling it to separate the different components. Oxygen boils at -183 °C, which is much colder than the other components of air, such as nitrogen and argon, so it can be easily separated from them.
Electrolysis of Water: Oxygen can be obtained by electrolyzing water. Water is composed of hydrogen and oxygen, and when an electric current is passed through it, the water molecules are broken down into hydrogen and oxygen gases. Oxygen is produced at the anode, and hydrogen is produced at the cathode.
Photosynthesis: Photosynthesis is a process that occurs in plants, algae, and some bacteria, in which light energy is converted into chemical energy. Oxygen is a byproduct of photosynthesis, which occurs when plants convert carbon dioxide and water into glucose and oxygen using energy from the sun.
Chemical Methods: Oxygen can also be obtained by chemical methods, such as the decomposition of hydrogen peroxide by manganese dioxide or the oxidation of potassium chlorate by concentrated sulfuric acid.
All the above methods are used to prepare oxygen on a laboratory scale, while in industry, the most commonly used method is the process of liquefaction and distillation of air. Oxygen is also obtained from air separation units (ASUs) which are used to produce high-purity oxygen for various industrial and medical applications.