Four elements - “chalcogen” (ie, “giving birth to copper”) lead the main subgroup of the VI group (according to the new classification - the 16th group) of the periodic system. In addition to sulfur, tellurium and selenium, oxygen also belongs to them. Let's take a closer look at the properties of this element most common on Earth, as well as the use and production of oxygen.
Element prevalence
The oxygen content in the earth's crust is almost 50%. It is found in various minerals in the form of oxides and salts.
In bound form, oxygen is included in the chemical composition of water - its percentage ratio is about 89%, as well as in the composition of the cells of all living things - plants and animals.
In air, oxygen is in a free state in the form of O2, occupying a fifth of its composition, and in the form of ozone - O3.
Physical properties
O2 is a gas that does not have color, taste or smell. It is slightly soluble in water. Boiling point - 183 degrees below zero Celsius. In liquid form, oxygen has a blue color, and in solid form it forms blue crystals. The melting point of oxygen crystals is 218.7 degrees below zero Celsius.
Chemical properties
When heated, this element reacts with many simple substances, both metals and non-metals, thus forming the so-called oxides - compounds of elements with oxygen. The chemical reaction in which elements enter with oxygen is called oxidation.
For instance,
4Na + O2 = 2Na2O
S + O2 = SO2
Some of the complex substances also react with oxygen, also forming oxides:
CH4 + 2O2 = CO2 + 2H2O
2CO + O2 = 2CO2
If any substance slowly reacts with oxygen, then such oxidation is called slow. For example, these are the processes of decomposition of food products, rotting.
Oxygen production
This chemical element can be obtained both in the laboratory and in an industrial enterprise.
Obtaining oxygen in the laboratory is carried out in several ways:
1. Using the decomposition reaction of bertoletova salt (potassium chlorate).
2. Through the decomposition of hydrogen peroxide when heated in the presence of manganese oxide, which acts as a catalyst.
3. Through the decomposition of potassium permanganate.
The production of oxygen in industry is carried out in the following ways:
1. For technical purposes, oxygen is obtained from air in which its usual content is about 20%, i.e. fifth part. To do this, the air is first burnt, obtaining a mixture with a liquid oxygen content of about 54%, liquid nitrogen - 44% and liquid argon - 2%. Then these gases are separated using the distillation process, using a relatively small interval between the boiling points of liquid oxygen and liquid nitrogen - minus 183 and minus 198.5 degrees, respectively. It turns out that nitrogen evaporates earlier than oxygen.
Modern equipment provides oxygen of any degree of purity. Nitrogen, which is obtained by separation of liquid air, is used as a raw material in the synthesis of its derivatives.
2. The electrolysis of water also gives oxygen of a very pure degree. This method has become widespread in countries with rich resources and cheap electricity.
Oxygen application
Oxygen is the main element in the vital activity of our entire planet. This gas, which is contained in the atmosphere, is consumed in the process of respiration by plants, animals and people.
Obtaining oxygen is very important for such areas of human activity as medicine, welding and cutting of metals, blasting, aviation (for breathing people and for engines), metallurgy.
In the process of human economic activity, oxygen is consumed in large quantities - for example, when burning various types of fuel: natural gas, methane, coal, wood. In all of these processes, carbon monoxide is formed. At the same time, nature provided for the process of natural binding of this compound using photosynthesis, which takes place in green plants under the action of sunlight. As a result of this process, glucose is formed, which the plant then spends to build its tissues.