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I. The Nature of oxygen
Oxygen is a colorless and odorless gas, which is slightly heavier than air. The solubility of oxygen in water is not large. 50mL of oxygen can be dissolved in 100mL water at 0℃, and only 3 ml can be dissolved in 20℃. Oxygen can condense into blue liquid under a certain pressure at-183℃. Many elements can react with oxygen.
The mixture of hydrogen and oxygen is explosive. The explosion limit of the hydrogen-oxygen mixture varies with the pressure, temperature and the content of water vapor. Under the atmospheric pressure, the explosion and liquid oxygen of its volume content are both refrigerants and oxidants, it is a relatively safe explosive material with the mixture of sawdust and coal powder. Pneumatic oxygen is usually stored in steel cylinders at 150 atmospheric pressure for transportation and use. Oxygen is a very important material in industry, scientific research, medical treatment and other aspects. The solubility of oxygen in water is 4.89 ml/100 ml water (℃), which is an important basis for the existence of life in water. Oxygen accounts for about 21% of the air volume.
II. The use of oxygen
Oxygen is the necessary gas for animals to breathe and burn combustibles. At first, oxygen was mainly used for medical oxygen therapy, oxygen delivery to rescue patients, and metal welding and cutting in the machinery industry. After that, with the continuous emergence of new technology and new technology, it will be gradually applied to metallurgy, petrochemical engineering, environmental protection and other departments. In metallurgical industry, oxygen is widely used in strengthening smelting of oxygen blowing converter, electric furnace and blast furnace; flame treatment on the surface of steel billets, etc. In petrochemical industry, oxygen is used to crack heavy oil, produce olefin gas or gasification heavy oil and coal dust, and prepare ammonia synthesis feed gas. In the aspect of environmental protection, oxygen can be used for air purification, urban sewage and wastewater treatment, etc.
III. Chemical properties
The methods of producing oxygen in industry are as follows: relatively pure oxygen produced by low temperature distillation; oxygen produced by electrolysis of water; oxygen produced by pressure changing adsorption, etc. The principle of producing oxygen is: the air after being compressed and dried by air compressor enters the PSA oxygen-nitrogen separation system, and the oxygen and nitrogen are separated by the adsorption of molecular sieve.
Another method of producing oxygen in the laboratory is to make use of the thermal decomposition of potassium chlorate. The reaction formula is:
MnO21
2KCLO2+ △ --- → 2KCL + 3O2
Oxygen molecules can generate hydrated crystals at low temperature: O2•H2O and O2•2H2O
The solid density of oxygen is 1.27 g/mL;
The gas density of oxygen is 1.429 g/mL;
The atomic volume of oxygen is 1.26 ml/mol;
Melting point is-218.99 ℃;
Boiling point is-183.0 ℃;
Critical temperature 119 ℃;
Oxygen is a kind of active chemical element. It can be combined with almost all other elements directly or indirectly. The product formed by the oxidation of one element is called oxide. The reason why oxygen is called oxidant is that when it reacts with elements, electrons are obtained, the oxidation number decreases from 0 to-2, and the oxygen itself is restored.
