Definition:
Oxygen, one of the main components of air, heavier than air, density of 1.429 g/liter under standard conditions (0 and atmospheric pressure of 101325 Pa). Colorless, odorless, tasteless. Solubility in water is very small. Pressure is 101kPa, oxygen in about -183 degrees Celsius when the light blue liquid, in about -218 degrees Celsius when the light blue solid into the snowflake.
Properties of oxygen:
1. Physical properties of oxygen:
(1) colorless and odorless, under standard conditions, the density of oxygen is 1.429g/L, the density is greater than that of air, it is difficult to dissolve in water, 1L of water can only be dissolved in about 30ml of oxygen.
(2) three-state change: oxygen (colorless gas) liquid nitrogen (light blue liquid) solid nitrogen (light blue snowflake)
(3) industrial production of oxygen, generally pressurized storage in blue cylinders.
2. Oxygen's chemical properties:
(1) more active chemical properties, under certain conditions, and a variety of substances can be chemical reactions, while releasing heat; with combustion and oxidizing, in the chemical reaction to provide oxygen, is a commonly used oxidant.
(2) Flammability, oxidizing
① Reaction with metals:
2Mg+O22MgO
3Fe+2O2Fe3O4
② Reaction with non-metals:
C+O2CO2 (O2 sufficient)
2C+O22CO (O2 not sufficient)
③ Reaction with compounds:
2CO+O22CO2
CH4+2O2CO2+2H2O
C2H5OH+3O22CO2+3H2O
Error Points:
(1) Mistakenly believe that oxygen is flammable and can be used as a fuel
Oxygen can help combustibles to burn, and it is a fuel. Oxygen can help combustible materials to burn and has flammability; it cannot burn itself and cannot be used as a combustible material.
(2) Misunderstanding that oxygen is very active chemically and can react with all substances
Oxygen is a very active gas chemically and can react chemically with many substances under certain conditions, but not with all substances.
(3) Misunderstanding that combustion requires oxygen
Combustion has a broad and narrow sense, usually referred to as combustion refers to combustibles and oxygen to a luminous, exothermic violent oxidation reaction. One of the conditions of combustion is the need for oxygen. But there are some combustion does not need oxygen, such as magnesium in carbon dioxide can also burn.
(4) Mistakenly believe that the reaction between substances and oxygen is called an oxidation reaction
Oxidation reaction is the reaction between substances and oxygen, including substances and oxygen in the oxygen reaction, but also includes substances and other oxygen-containing substances in the oxygen reaction. For example, the reaction of hydrogen with oxygen to form water is an oxidation reaction, and the reaction of hydrogen with copper oxide to form copper and water is also an oxidation reaction.
(5) Mistakenly believe that the properties of oxygen and liquid oxygen do not work
The properties of a substance include physical properties and chemical properties, and the physical properties of oxygen and liquid oxygen are different, but the chemical properties are the same, because both of them have the same molecular composition, and they are both made up of oxygen molecules.
(6) It is mistakenly believed that oxygen can be made from any substance containing oxygen.
Oxygen-containing substances are needed to make oxygen, but not all oxygen-containing substances can be used to make oxygen. Uses of Oxygen
Uses:
1. Smelting process In the process of steelmaking, blowing high purity oxygen, oxygen and carbon and phosphorus, sulfur, silicon and other oxidation reaction, which not only reduces the carbon content of steel, but also conducive to the removal of phosphorus, sulfur, silicon and other impurities. And the heat generated in the oxidation process is enough to maintain the temperature required for the steelmaking process, therefore, oxygen blowing not only shortens the smelting time, while improving the quality of steel. In blast furnace ironmaking, increasing the oxygen concentration in the blast air can reduce the coke ratio and increase the output. In non-ferrous metal smelting, the use of oxygen-enriched can also shorten the smelting time to improve production.
2. Chemical industry
In the production of ammonia, oxygen is mainly used for the oxidation of raw gas to strengthen the process and increase the yield of fertilizer. Another example is the high temperature cracking of heavy oil, and the gasification of pulverized coal.
3. Defense industry
Liquid oxygen is the best fuel for modern rockets, in supersonic aircraft also need liquid oxygen as an oxidizer, combustible substances impregnated with liquid oxygen has a strong explosive, can make liquid oxygen explosives.
4. Medical care
Supply respiration: Used for hypoxia, low oxygen or anoxic environment, such as: diving, mountaineering, high-altitude flight, cosmic voyage, medical rescue and so on.
5. Other
such as: it itself as a flux with acetylene, propane and other flammable gases used in conjunction to achieve the role of welding and cutting metal, in various industries, especially in the mechanical enterprises are widely used as a cutting of the use is also very convenient, it is the preferred method of a cutting.
Excessive inhalation of oxygen negative effects:
As early as the mid-19th century, the British scientist Paul Burt first discovered that if the animals breathe pure oxygen will cause poisoning, humans are the same. Oxygen cylinders oxygen cylinders people if greater than 0.05MPa (half an atmosphere) in the pure oxygen environment, all the cells have a toxic effect, inhalation time is too long, it may occur "oxygen poisoning". The capillary barrier of the lungs is destroyed, leading to pulmonary edema, pulmonary bruising and hemorrhage, seriously affecting respiratory function, and then the organs are damaged by oxygen deprivation. In a pure oxygen environment of 0.1MPa (1 atmosphere), a person can only survive for 24 hours before pneumonia occurs, which eventually leads to respiratory failure and death by asphyxiation. In 0.2MPa (2 atmospheres) high-pressure oxygen environment, people can stay up to 1.5 hours to 2 hours, more than will cause brain poisoning, life rhythm disorder, mental disorganization, memory loss. If you add 0.3MPa (3 atmospheres) or even higher oxygen, brain cell degeneration and necrosis will occur within minutes, convulsions and coma, resulting in death.
In addition, excessive oxygen intake also promotes life aging. Oxygen into the human body and cell oxidase reaction, can generate hydrogen peroxide, and then into lipofuscin. This lipofuscin is a harmful substance that accelerates cellular aging, and it accumulates in the heart muscle, making cardiomyocyte aging, heart function decline; accumulates in the blood vessel wall, causing blood vessel aging and hardening; accumulates in the liver, weakening the liver function; accumulates in the brain, causing intellectual decline, memory loss, and the person becomes demented; accumulates in the skin, forming the age spots.
The effects of oxygen deficiency and oxygen enrichment on the human body:
Oxygen concentration (% volume) - signs (at atmospheric pressure)
100% - fatal / 6 minutes;
50% - fatal / 4-5 minutes can be cured by treatment
> 23.5% - oxygen enrichment, with a strong risk of explosion
20.9% - normal oxygen concentration
19.5% - minimum permissible concentration of oxygen
15-19% - reduces efficiency and can cause head, lung and circulatory problems
10-12% - shortness of breath, loss of judgment, purple lips
8-10% - loss of mental capacity, fainting
6-8% --- 8 minutes;
4-6% --- convulsions within 40 seconds, respiratory arrest, death
Oxygen industrial production method
Industrial production of oxygen:
Oxygen production in the laboratory is commonly used in the decomposition of hydrogen peroxide or potassium permanganate to produce oxygen, with a fast reaction, The method is characterized by fast reaction, easy operation and easy collection, but the cost is high and it can't be produced in large quantities, so it can only be used in the laboratory. For industrial production, it is necessary to consider whether the raw material is easy to obtain, whether the price is cheap, whether the cost is low, whether it can be produced in large quantities, and the impact on the environment. Air contains about 21% of oxygen, which is a cheap and easily available raw material for the production of oxygen. Industrial Oxygen Production
Industrial Oxygen Production Methods:
1, Air Freezing Separation Method
The main components of air are oxygen and nitrogen. Utilizing the different boiling points of oxygen and nitrogen, the preparation of oxygen from the air is called air separation method. The air is first pre-cooled, purified (to remove a small amount of moisture in the air, carbon dioxide, acetylene, hydrocarbons and other gases and dust and other impurities), and then compressed, cooled, so that it becomes liquid air. Then, the use of oxygen and nitrogen boiling point of the different, in the distillation tower in the liquid air evaporation and condensation, the oxygen and nitrogen separation, to get pure oxygen (can reach 99.6% purity) and pure nitrogen (can reach 99.9% purity). If you add some additional devices, you can also extract argon, neon, helium, krypton, xenon and other rare inert gases in the air content is very small. Oxygen produced by the air separation device, through the compressor compression, and finally the compressed oxygen will be loaded into high-pressure cylinder storage, or through the pipeline directly to the factory, workshop use. The use of this method of producing oxygen, although it requires large sets of equipment and strict safety operation techniques, but the output is high, every hour can produce several dry, ten thousand cubic meters of oxygen, and the raw materials consumed just do not have to buy, do not have to transport, do not have to warehouse storage of air, so from 1903 to develop the first deep-cooled air separation of the oxygen machine since this method of oxygen production has been the most widely used.
2, molecular sieve oxygen method (adsorption method)
The use of nitrogen molecules greater than the characteristics of oxygen molecules, the use of special molecular sieve to separate the oxygen in the air. First of all, the compressor forced dry air through the molecular sieve into the vacuum adsorber, the nitrogen molecules in the air that is adsorbed by the molecular sieve, the oxygen into the adsorber, when the adsorber oxygen reaches a certain amount (the pressure reaches a certain level), you can open the valve to release the oxygen. After a period of time, the molecular sieve adsorption of nitrogen gradually increased, the adsorption capacity is weakened, the output of oxygen purity decreased, the need to use a vacuum pump to pump out the adsorption in the molecular sieve above the nitrogen, and then repeat the above process. This method of producing oxygen is also called adsorption method. The use of adsorption method of oxygen small oxygen concentrator has been developed, easy to use at home.