Overview:
Chinese name: oxygen
1. Physical properties
Description: color, taste and state: colorless and odorless gas (standard state)
(2) melting point: -2 18.4℃ (turning into a blue snowflake solid) boiling point:-182.9℃ (turning into a light blue liquid).
③ Density: 1.429g/L (gas), 1.4 19g/cm3 (liquid), 1.426g/cm3 (solid).
④ Water solubility: insoluble in water. Under standard conditions, about 30mL of oxygen can be dissolved in 1L water.
⑤ Storage: sky blue steel cylinder
2. Chemical properties
Generally speaking, oxygen is more active chemically.
(1), reaction between oxygen and metal:
Reaction with potassium:
4K+O2=2K2O, the surface of potassium darkens.
2K+O2 = K2O 2； K+O2=KO2 (potassium peroxide), (conditions: ignition or heating, two reactions at the same time)
Reaction with sodium:
4Na+O2=2Na2O, the surface of sodium darkens.
2Na+O2=Na2O2 (condition: ignition or heating), yellow flame is generated, and a large amount of heat is released to generate light yellow powder.
React with magnesium; 2 mg+O2 = 2 MgO (condition: ignition), intense combustion gives off dazzling light, releases a lot of heat, and generates white solid.
Reaction with aluminum; 4al+3o2 = 2al2o3 (condition: ignition), giving off light and heat to generate white solid.
React with iron;
4 Fe+3 O2+2 xh2o = 2 Fe2O3 H2O (formation of rust)
3Fe+2O2 = Fe3O4 (condition: ignition), the red-hot iron wire burns violently, and sparks radiate, releasing a lot of heat and generating black solids.
Reaction with zinc: 2Zn+O2=2ZnO (condition: ignition),
Reaction with copper; 2cu+O2 = 2cuo (condition: heating). After heating, a layer of black substance is formed on the surface of bright red copper wire.
(2), oxygen and nonmetal reaction:
Reaction with hydrogen: 2H2+O2=2H2O (condition: ignition), producing light blue flame, releasing a lot of heat and generating water.
Reaction with carbon: CO2 (carbon dioxide)
(carbon+oxygen → carbon dioxide) C+O2 = CO2 (condition: fire), which burns violently, emits white light, releases heat, and produces gas to make limewater turbid.
When oxygen is incomplete, carbon monoxide is produced: 2C+O2=2CO (condition: fire).
Reaction with sulfur: S+O2 = SO2 (condition: ignition), bright blue-purple flame, heat release, and gas with pungent smell. This gas can also make clear limewater turbid and discolor acidic potassium permanganate solution or magenta solution.
Reaction with red phosphorus: 4p+5o2 = p4o 10 (condition: fire), intense combustion, luminescence and exotherm, white smoke. (P4O 10 is the molecular formula of phosphorus pentoxide, and P2O5 can be written here. )
Reaction with white phosphorus: P4+5O2=P4O 10, white phosphorus spontaneously ignites in the air, emits light and produces white smoke.
Reaction with nitrogen: N2+O2=2NO (condition: discharge)
Reaction with oxygen: 3O2=2O3 (condition: discharge)
(3) Oxygen reacts with some organic substances, such as methane, acetylene, alcohol, paraffin, etc. When burned in oxygen, water and carbon dioxide can be generated.
The combustion of gaseous hydrocarbons usually emits a bright blue flame, releasing a lot of heat, producing water and gas, which can make clear limewater turbid.
Methane: CH4+2O2 → CO2+2H2O (condition: ignition)
Ethylene: C2H4+3O2→2CO2+2H2O (condition: ignition)
Acetylene: 2c2h2+5o2 → 4co2+2h2o (condition: ignition)
Benzene: 2c6H6+15o2→12co2+6H2O (condition: ignition)
Methanol: 2ch2 oh+3 O2→2 CO2+4H2O (condition: ignition)
Ethanol: CH3CH2OH+3O2→2CO2+3H2O (condition: ignition)
The general formula for the combustion of hydrocarbons and oxygen is 4cxhyoz+(4x+y-2z) O2→ 4x CO2+2yh2o (condition: ignition) (please pay attention to simplification after completion of the general formula! The same below)
The general combustion formula of hydrocarbons is 4CxHy+(4x+y)O2→4xCO2+2yH2O (condition: ignition).
Ethanol is oxidized by oxygen: 2CH3CH2OH+O2→2CH3CHO+2H2O (condition: Cu, heating).
This reaction includes two steps: (1)2Cu+O2=2CuO (heating) (2)CH3CH2OH+CuO→CH3CHO+Cu+H2O (heating).
The reaction between chloroform and oxygen: 2CHCl3+O2→2COCl2 (phosgene) +2HCl.
(4), the reaction of oxygen and other compounds:
Hydrogen sulfide combustion: (completely) 2h2s+3o2 = 2h2o+2so2; (Incomplete) 2H2S+O2=2H2O+2S (condition: ignition)
Calcined pyrite: 4fe2+11O2 = 2fe2o3+8so2 (condition: high temperature).
Catalytic oxidation of sulfur dioxide: 2SO2+O2=2SO3 (conditions: V2O5, heating)
Formation of sulfuric acid rain in air: 2SO2+O2+2H2O=2H2SO4.
Combustion of ammonia in pure oxygen: 4NH3+3O2 (pure) =2N2+6H2O (condition: ignition).
Catalytic oxidation of ammonia: 4NH3+5O2=4NO+6H2O (conditions: Pt, heating).
The reaction between nitric oxide and oxygen: 2NO+O2=2NO2.
Second, some uses and negative effects of oxygen
1. Melting process
High-purity oxygen is introduced during steelmaking, which reacts with carbon, phosphorus, sulfur and silicon, which not only reduces the carbon content in steel, but also helps to remove impurities such as phosphorus, sulfur and silicon. Moreover, the heat generated in the oxidation process is enough to maintain the temperature required in the steelmaking process, so blowing oxygen not only shortens the smelting time, but also improves the quality of steel. In blast furnace ironmaking, increasing the oxygen concentration in blast furnace can reduce the coke ratio and increase the output. In nonferrous metal smelting, oxygen enrichment can also shorten smelting time and increase output.
2. Chemical industry
In the production of synthetic ammonia, oxygen is mainly used for the oxidation of feed gas, such as pyrolysis of heavy oil and gasification of pulverized coal, in order to strengthen the process and increase the yield of chemical fertilizer.
3. Defense industry
Liquid oxygen is the best combustion improver for modern rockets, and it is also the oxidant needed in supersonic aircraft. Combustible substances are highly explosive after being impregnated with liquid oxygen, which can be used to make liquid oxygen explosives.
4. Health care
Supply breathing: used for hypoxia, hypoxia or no
Oxygen environment, such as diving, mountain climbing, high-altitude flight, space navigation, medical rescue, etc.
Oxygen is the "power source" of the heart.
Oxygen is the key substance of human metabolism and the first need of human life activities. Breathing oxygen is converted into available oxygen in human body, which is called blood oxygen. Blood carries blood oxygen to input energy to the whole body, and the delivery of blood oxygen is closely related to the working state of the heart and brain. The stronger the pumping ability of the heart, the higher the blood oxygen content; The stronger the blood transfusion ability of the coronary artery of the heart, the higher the blood oxygen concentration delivered to the heart, brain and whole body, and the better the running state of important organs of the human body.
Two. Oxygen fountain
With the increasing demand for fresh oxygen, oxygen fountain bars have been established in big cities such as Los Angeles. In the oxygen fountain bar, people hold transparent oxygen bottles with exquisite external suction devices. With a gentle suction, pure oxygen in the bottles will gush out. Oxygen with lemon or other fragrance can be continuously delivered for 20 minutes. In addition, other oxygen-related products in the United States are constantly emerging, such as various oxygenated water, oxygenated soda water, oxygenated capsules and so on. Emerging oxygen consumption has formed a new trend.
3. Increasing oxygen intake can reduce postoperative infection and stop vomiting.
The American New England Journal of Medicine published a new research result. Anesthesiologists in Austria, the United States and Australia report that the risk of postoperative infection will be reduced by half as long as the oxygen intake is increased during and after operation. Because increasing oxygen can improve the immune ability of the immune system, it can provide more ammunition for the patient's "immune army" and kill bacteria in the wound.
The study was conducted on 500 patients in hospitals in Vienna, Austria and Hamburg, Germany. 250 patients in the first group were anesthetized with 30% oxygen during the whole operation and 2 hours after operation, while 250 patients in the other group were anesthetized with 80% oxygen at the same time. Results There were 28 postoperative infections in the first group, but only 13 postoperative infections in the second group.
Nausea or vomiting after anesthesia is quite common and patients feel very uncomfortable. The anesthesiologist who conducted this study said that increasing the amount of oxygen inhalation was effective, harmless and cheap compared with all antiemetic drugs used up to 2009. The mechanism of oxygen preventing vomiting may be to prevent intestinal ischemia, thus preventing the release of emetic factors. However, it is not advisable to completely replace nitric oxide with oxygen, because it may wake up the patient during the operation.
4. Hyperbaric oxygen therapy for sudden deafness
According to the director of hyperbaric oxygen department in a hospital, hyperbaric oxygen can not only improve the anoxic state of hearing organs in the inner ear, but also improve the blood circulation of the inner ear, that is, tissue metabolism, and promote the recovery of hearing function. Once you suffer from sudden deafness, you should go to the hyperbaric oxygen department of the hospital immediately, because the curative effect of hyperbaric oxygen on sudden deafness often depends on the initial treatment time, and generally the best treatment effect is within three days (not later than one week) after onset.
5. Hyperbaric oxygen has a good effect on periodontal disease.
Periodontal disease refers to inflammation, deformation and atrophy of gingiva, periodontal ligament and alveolar bone, which eventually leads to tooth loosening and falling off. With periodontal disease, there will be gingival congestion, redness, bleeding and deepening of gingival sulcus, which will lead to periodontitis, periodontal pocket overflow, bad breath, loose teeth, and often accompanied by gingival recession.
The conventional treatment effect of periodontal disease is not ideal. In recent years, medical workers have used hyperbaric oxygen to treat periodontal diseases and achieved good results. Hyperbaric oxygen therapy can increase the oxygen content and diffusion distance of periodontal tissue, promote the reconstruction of collateral circulation and improve local circulation. Vasoconstruction can relieve local swelling. In addition, hyperbaric oxygen can effectively inhibit the growth and reproduction of bacteria, especially anaerobic bacteria, improve the blood supply and oxygen supply to periodontal tissues, promote metabolism, facilitate the repair of local tissues, and achieve the purposes of anti-inflammation, detumescence, hemostasis and deodorization.
Six, middle-aged and elderly people need to supplement oxygen.
Hypoxia is generally divided into two types: one is hypoxia in vitro and the other is hypoxia in vivo:
Hypoxia in vitro: Hypoxia mainly caused by external reasons. People living in anoxic environment, such as low cloudy weather, plateau areas, environmental pollution areas, office buildings, shopping malls, basements, etc. It is easy to lack oxygen in vitro.
Hypoxia in the body: refers to the lack of oxygen inhalation caused by the human body itself, which is related to some senile diseases, fast work pace and other reasons. Such as respiratory diseases (tracheitis, asthma, emphysema, cor pulmonale, pulmonary infection, etc.). ); Poor blood circulation (various heart diseases, cerebral ischemia, cerebral infarction, vasculitis, varicose veins, etc. ). Long-term hypoxia in the body, hypoxia in human tissues, accelerating body failure, and even causing accidents such as stroke, directly threatening life safety.
Hypoxia symptoms in middle-aged and elderly people
1) Mild hypoxia: yawning, cold hands and feet, chest tightness and shortness of breath, palpitation and shortness of breath in large shopping malls and underground facilities.
2) Moderate hypoxia: chest tightness, shortness of breath, shortness of breath when climbing more than two stairs; Bad breath, hyperacidity, constipation, dry skin, lack of sleep, dreaminess, easy to wake up, inattention, pallor, increased dandruff after tension, sweating, decreased vision, high blood pressure, blood lipid and blood sugar, weakened resistance and easy to catch a cold.
Seven. Negative effects of excessive inhalation of oxygen
As early as the middle of19th century, British scientist Paul Burt first discovered that if animals breathe pure oxygen, it will cause poisoning, and so will humans. If people are exposed to pure oxygen with a concentration exceeding 0.05 MPa (half atmospheric pressure), it is toxic to all cells. If the inhalation time is too long, "oxygen poisoning" may occur. The capillary barrier of the lung is destroyed, which leads to pulmonary edema, pulmonary congestion and bleeding, which seriously affects the respiratory function, and then causes hypoxia and damages the expanders. In the pure oxygen environment of 0. 1 MPa( 1 atmospheric pressure), people can only survive for 24 hours, and pneumonia will occur, which will eventually lead to respiratory failure and suffocation. People who stay in the high-pressure pure oxygen environment of 0.2 MPa(2 atmospheres) for at most 1.5 to 2 hours will cause brain poisoning, life rhythm disorder, mental disorder and memory loss. If 0.3 MPa(3 atmospheres) or even higher oxygen is added, people will experience brain cell degeneration and necrosis, convulsion and coma within a few minutes, leading to death.
In addition, excessive oxygen inhalation will also promote life aging. Oxygen entering the human body reacts with oxidase in cells to generate hydrogen peroxide, which in turn becomes lipofuscin. This lipofuscin is a harmful substance that accelerates cell aging, accumulates in myocardium, ages myocardial cells and reduces heart function. Accumulation on the wall of blood vessels leads to aging and hardening of blood vessels; Accumulate in the liver and weaken liver function; Accumulate in the brain, causing mental decline and memory decline, and people become dementia; Accumulate on the skin and form senile plaques.
[Edit this paragraph] III. Oxygen manufacturing
General laboratory oxygen production methods are:
Experimental device
1. heating potassium permanganate, chemical formula: 2kmno4 = = (△) k2mno4+MnO2+O2 =
2. Using MnO2 as catalyst, heating potassium chlorate, the chemical formula is 2kclo3 = = (△, MnO2) 2kcl+3o2 =
3. Hydrogen peroxide (hydrogen peroxide) generates O2 and H2O in the catalyst MnO2 (or red brick powder, potatoes, cement, etc.). ), the chemical formula is: 2h2o2 = = (MnO2) 2h2o+O2 =
Methods for industrial production of oxygen;
1. compressed cooling air
2. Molecular sieve
Oxygen production method of nuclear submarine: 2na2o2+2co2 = = 2na2co3+O2 ↑ Advantages of this method: 1, room temperature; 2. Circulate oxygen and carbon dioxide (people consume oxygen and exhale carbon dioxide, but this reaction consumes carbon dioxide and produces oxygen).
[Edit this paragraph] 4. The discovery of oxygen
The earliest discovery of oxygen in the world was made by alchemists and horses in the Tang Dynasty in China. After carefully observing the combustion of charcoal, sulfur and other combustible materials in the air, Ma and Ma came to the conclusion that the composition of air is complex, mainly composed of Yang (nitrogen) and Yin (oxygen), of which Yang is much more than Yin, which can be combined with combustible materials to remove it from the air, while Yang Can is still safely left in the air. Ma further pointed out that it exists in copper sulfate (oxide), nitrate and other substances. If you heat them with fire, they will be released He also thinks that there is a lot of yin in the water, but it is often difficult to take it out. The horse was discovered earlier than Europe 1000 years ago.
Ma He recorded his lifelong research achievements in a book named Ping Long's Memory, which was 68 pages long and published on March 9, the first year of the Tang Dynasty to Germany (756). It spread to the Qing Dynasty and was taken away by the German invaders.
1774, the British chemist J. priestley and his companions focused sunlight with a convex lens, and then heated mercury oxide to produce pure oxygen. It was found that pure oxygen supported combustion and helped breathing, which was called "dephosphorized air". Sweden's C.W. Scheler made oxygen by heating mercuric oxide and other oxyacid salts one year earlier than priestley, but his paper "Chemistry on Air and Fire" was not published until 1777, but they did make oxygen independently. 1774, priestley visited France and told A.-L. lavoisier how to make oxygen. The latter repeated the experiment in 1775 and called the gas in the air oxygen, which comes from the Greek word oxygen and means "acid producer". So these three scholars are all recognized oxygen discoverers in later generations.
[Edit this paragraph] V. Determination of oxygen volume fraction in air
Name: Red Phosphorus Combustion Experiment
Principle: Red phosphorus is burned in a closed container, and the volume fraction of oxygen in the air is determined.
Red phosphorus+oxygen = (ignite) phosphorus pentoxide
4P+5O2= (ignite) 2P2O5
Equation: 4P+5O2= ignition =2P2O5.
Phenomenon: red phosphorus: yellow flame and white smoke give off heat.
Water enters the gas container along the conduit and stops at about one fifth.
Conclusion: 1 Oxygen accounts for about one fifth of the air volume (principle) (1. Oxygen is insoluble in water. 2. Nitrogen is nonflammable and does not support combustion).
Note: Red phosphorus can be replaced by other substances, but the product must not be gas and can only react with oxygen.
The key to success: good air tightness, otherwise the result is small.
The amount of red phosphorus should be enough, otherwise the result will be too small.
Wait until the equipment is completely cooled before opening the water stop clip, otherwise the effect will be very small.
Add a water stop clip before the experiment starts, otherwise the result will be too big.
[Edit this paragraph] VI. oxygen
A chemical element. Chemical symbol o, atomic number 8, atomic weight 15.9994, belongs to ⅵ a group in the periodic table. )
Discovery of oxygen 1774 British chemist J. priestley and his companions focused sunlight with a convex lens, and then heated mercury oxide to produce pure oxygen. It was found that pure oxygen supported combustion and helped breathing, which was called "dephosphorized air". Sweden's C.W. Scheler made oxygen by heating mercuric oxide and other oxyacid salts one year earlier than priestley, but his paper "Chemistry on Air and Fire" was not published until 1777, but they did make oxygen independently. 1774, priestley visited France and told A.-L. lavoisier how to make oxygen. The latter repeated the experiment in 1775 and called the gas in the air oxygen, which comes from the Greek word oxygen and means "acid producer". So these three scholars are all recognized oxygen discoverers in later generations.
There are three stable isotopes of oxygen, namely oxygen 16, oxygen 17 and oxygen 18, among which the content of oxygen 16 accounts for 99.759%. The content of oxygen in the crust is 48.6%, ranking first. Oxygen is widely distributed on the earth, accounting for 20.95% in the atmosphere, and oxygen compound water is everywhere in oceans, rivers and lakes, accounting for 88.8% in water. There are many oxygenated salts on the earth, such as aluminosilicate contained in soil, and minerals such as silicate, oxide and carbonate. Oxygen in the atmosphere is constantly used for animal metabolism, and oxygen in human body accounts for 65%. Photosynthesis of plants can convert carbon dioxide into oxygen, which keeps the oxygen circulating. Although the earth is full of oxygen, it is mainly extracted from the air and there are inexhaustible resources.
Oxygen is a chemically active element. Except chlorine, bromine, iodine and some inert metals (such as gold and platinum) in inert gases and halogens, most nonmetals and gold metals can be directly combined with oxidation, but oxygen can react with the inert gas xenon to generate oxides through indirect methods:
XeF6 + 3H2O=XeO3 + 6HF
Similarly, chlorine oxide can also be prepared by indirect methods:
2Cl2+2HgO=HgO？ Mercury chloride+chlorite oxide
At room temperature, oxygen can also oxidize other compounds:
2NO+O2=2NO2
Oxygen can oxidize glucose, which is the main reaction that constitutes organism respiration:
C6H 12O6+6O2=6CO2+6H2O
The oxidation states of oxygen are -2,-1 and +2. The oxidation of oxygen is second only to that of fluorine, so when oxygen reacts with fluorine, it appears with a valence of +2, forming oxyfluoride (F2O). The binary compounds formed by oxygen and metal elements are oxides, peroxides and superoxides. Oxygen molecules can lose an electron, generating molecular oxygen (), forming compounds such as O2PtF6.
The laboratory preparation methods of oxygen are as follows: ① thermal decomposition of potassium chlorate:
(2) Electrolytic water:
③ Thermal decomposition of oxides:
(4) using manganese dioxide as a catalyst to decompose hydrogen peroxide;
⑤ Thermal decomposition of potassium permanganate
In the spacecraft, the carbon dioxide gas exhaled by astronauts can react with potassium peroxide to produce oxygen for astronauts to breathe.
The method of large-scale production and application of oxygen is fractionation of liquid air. First compress the air, then freeze it into liquid air. Because the boiling points of rare gases and nitrogen are lower than that of oxygen, the remaining liquid oxygen after fractionation can be stored in high-pressure steel cylinders. All oxidation reactions and combustion processes need oxygen, such as removing impurities such as sulfur and phosphorus during steelmaking. When the mixture of oxygen and acetylene burns, the temperature is as high as 3500℃, which is used for welding and cutting steel. Oxygen is needed for glass manufacturing, cement production, mineral roasting and hydrocarbon processing. Liquid oxygen is also used as rocket fuel, which is cheaper than other fuels. People who work in anoxic or anoxic environment, such as divers and astronauts, oxygen is indispensable to maintain life. However, the active state of oxygen, such as OH and H2O2, has serious damage to biological tissues, and the damage of ultraviolet rays to skin and eyes is mostly related to this effect. It is one of the components of air, colorless, odorless and tasteless. The density of oxygen is higher than that of air, and it is 10 1325pa under standard conditions (0℃, atmospheric pressure) .429g/l. It is soluble in water, but the solubility is very small. About 30mL of oxygen can be dissolved in 1L water. When the pressure is 10 1kPa, oxygen turns into a light blue liquid at about-180℃ and turns into a snowy light blue solid at about -2 18℃.
1. Oxygen can directly combine with many elements to form oxides.
2. Oxygen is a necessary gas for animals and plants to burn and breathe. Oxygen-enriched air is used for medical treatment and high-altitude flight, pure oxygen is used for steelmaking, cutting and welding metals, and liquid oxygen is used as oxidant for rocket engines.
3. Oxygen used in production is fractionated from liquid air.
4. An oxygen molecule consists of two oxygen atoms with an atomic radius of 0.074 nm.
5. The chemical reaction between substance and oxygen belongs to compound reaction.