Discovery of oxygen 1774 British chemist J. priestley focused sunlight with a large 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 265,438+0% 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.
Physical and physical properties: Oxygen is a colorless, odorless and tasteless gas with a melting point of -2 18.4℃, a boiling point of-182.962℃, a gas density of 1.429 g/cm3, and liquid oxygen is light blue.
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 fluorine, so when oxygen reacts with fluorine, it appears as +2 valence, 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. Oxygen is produced by the decomposition of oxygen-containing salts (potassium chlorate, potassium permanganate, etc.). ) by heating in the laboratory.
4. An oxygen molecule consists of two oxygen atoms with an atomic radius of 0.074 nm.
Edit this paragraph 2, the nature of oxygen.
1. Physical properties:
① Color, taste and state: colorless and odorless gas (standard state)
(2) Melting point: -2 18.4℃ (turning into light blue snowflake solid) Boiling point:-182.9℃ (turning into 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:
Magnesium monoxide; 2 mg+O2 → 2 MgO, intense combustion gives off dazzling light, releases a lot of heat, and produces white solid.
Ferroferric oxide; 3Fe+2O2 → Fe3O4, the red-hot iron wire burns violently and sparks everywhere, releasing a lot of heat and generating black solids.
Copper monoxide; 2cu+O2 → 2cuo, which forms a layer of black substance on the surface of bright red copper wire after heating.
Sulfur dioxide; S+O2→SO2, when ignited, emits a blue-purple flame, releases heat and produces a pungent smell.
(2), oxygen and nonmetal reaction:
(carbon+oxygen → carbon dioxide) C+O2 → CO2, burning violently, emitting white light and heat, and producing gas that makes limewater turbid.
S+O2 → SO2 produces bright blue-purple flame, releases heat and produces gas with pungent smell.
4p+5o2 → 2p2o5, burning violently, emitting strong light, releasing heat and producing white smoke.
(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.
CH4+2O2→2CO2+2H2O
2C2H2+5O2→4CO2+2H2O
Edit the third paragraph. Some uses and negative effects of oxygen
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.
In June+10 this year, 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 the study said that increasing the amount of oxygen inhalation is effective, non-dangerous and low-cost. 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 even sudden deafness
According to the director of hyperbaric oxygen department of Friendship 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 paragraph 4: oxygen manufacturing
The general method of making oxygen in the laboratory is to heat potassium permanganate, with the chemical formula: 2kmno4 = = (heating) k2mno4+MnO2+O2 =
Another method is to heat potassium chlorate with catalyst MnO2, and the chemical formula is 2kClO3 = = (△, MnO2) 2kCl+3o2.
The other is that hydrogen peroxide (hydrogen peroxide) generates O2 and H2O in MnO2 (or red brick powder, potatoes, cement, etc.). ), the chemical formula is: 2h2o2 = = (MnO2) 2h2o+O2 ↑.
The method of industrial production of oxygen: separating liquid air.
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.
Edit the discovery of oxygen in paragraph 5 of this paragraph.
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.