Oxygen is a simple substance formed by oxygen element, chemical formula OtwoIts chemical properties are relatively active, and most elements can react with oxygen.It is not very active at room temperature, and is not easy to interact with many substances.However, it is very active at high temperature and can combine with many elements directly, which is second only to the electronegativity of oxygen atomfluorineof[1-2]
Oxygen is colorless and tastelessGas, YesOxygen elementMost commonSimple substanceform.melting point-218.4 ℃, boiling point - 183 ℃.It is insoluble in water, and about 30mL oxygen is dissolved in 1L water.Oxygen accounts for about 21% in the air.liquid oxygenIt is sky blue.The solid oxygen is blue crystal.
Oxygen is the most widely distributed in nature, accounting forCrust48.6% of the mass is the highest abundance element.stayHydrocarbonsOxygen is required for oxidation of oxygen, wastewater treatment, rocket propellant, and breathing of animals and people in aviation, aerospace and diving.Animal respiration, combustion and all oxidation processes (includingOrganic compound) consume oxygen.But the oxygen in the air can be continuously supplemented through the photosynthesis of plants.In metal cutting and welding.Oxygen and combustible gas with purity of 93.5%~99.2% (such asacetylene）Mix to produce a flame of extremely high temperature, thus melting the metal.The metallurgical process is inseparable from oxygen.To strengthennitric acidandsulphuric acidOxygen is also needed in the production process of.Use oxygen instead of airsteamWhen the mixture is blown into the gas gasifier, high calorific value gas can be obtained.Medical gas is extremely important.
Chinese name
oxygen
Foreign name
oxygen
chemical formula
O₂
molecular weight
thirty-two
CAS login number
7782-44-7
EINECS login number
231-956-9
Melting point
-218.4 ℃
Boiling point
-183 ℃
Water solubility
Insoluble in water, slightly soluble in alcohol[3]
Priestley calcined from BlacklimestoneyesCO2Inspired by his discovery, he used a convex lens to focus sunlight to make some substances burn or decompose to release gas and conduct research.On August 1, 1774, Priestley finally succeeded in producing oxygen, which became a significant event in the history of chemistry.
His experiment was very simple. He put mercury oxide in a glass bottle filled with mercury, and then inverted the glass bottle into the mercury tank. The glass bottle was completely filled with mercury, and the air was completely removed,Mercuric oxideFloat on top.Then, he used a convex lens to focus the sunlight on the mercury oxide, so that the mercury oxide was heated.
After long-term heating, the temperature gradually rises, and mercury oxide is heated to decompose into mercury and release oxygen.As a result, oxygen accumulates and discharges the mercury in the glass bottle, reducing the mercury level.The volume of the gas space continues to increase until the volume of the gas is three or four times the volume of mercury oxide.The reaction equation is:
However, at the beginning, he did not know that the pure gas produced was oxygen.Nevertheless, careful Priestley did many more experiments to understand the nature of this gas and its difference from other "air".His research methods are:
1. He put the studied gas into a glass bottle and poured some water into it, but the gas was insoluble.
2. He put the burning candle into the gas, and the candle gave off a bright light.
3. He put a mouse into a bottle filled with the gas. The mouse was alive and well, and he guessed that people might feel better if they inhaled it.
4. He sucked the oxygen in the large bottle into his lungs with a glass tube and wrote down his feelings: "I feel very happy. My lungs feel as if I am breathing the air normally, without any discomfort. Moreover, after inhaling this gas for a long time, my body is still very relaxed and happy. Maybe one day, who can decide that this gas will not become a fashionable luxury?however.There are only two mice and myself in the world who can enjoy the pleasure of this gas. "
Proctor obtained from the above experiments that the gas has combustion supporting and breathing supporting effects, which are similar to ordinary air, but have stronger effects.But he mistakenly used oxygen, a new gasPhlogiston theoryThe oxygen produced is called "deflagration air".Due to the wrong theory, this naming is inappropriate.
After Carl Wilhelm Scheler studied air in 1772, he first realized that oxygen is an important component of air.He mixed sulfur and iron powder, burned them in the air, and consumed the oxygen in the air in the bell jar to produce nitrogen. At that time, he called it "turbid gas" or "used air", or a gas that can kill people.
After thinking, Scheler realized that the idea that air was an element at that time was wrong.He conjectured that air is a mixture of two different substances. One is turbid air, which can kill people;One is the air that can make people live. It can help to burn and disappear in the burning.So Scheler became interested and began his experiment.
In 1773, he put saltpeter (KNOthree）LoadingCurved neck bottleThe mouth of the bottle is tied with a pig bladder that has exhausted the air, and then the curved neck bottle is put on the stove to burn.When saltpeter melts, it decomposes and gives off a kind of gas, which soon fills the pig bladder. This gas is just the kind of gas that can live, namely oxygen.
Scheler made a careful identification. He threw the red hot charcoal into a bottle full of "living gas", and the charcoal burned quickly and brightly, burning faster and brighter than in ordinary air.Scheler mixed 1/5 of this gas and 4/5 of the turbid gas in the bottle, the candle could burn normally, and the mice also breathed in the ordinary air.From this he determined that the gas was a pure gas that could live.
Lavoisier's discovery of oxygen was inspired by Priestley.In 1774, Lavoisier made oxygen from the synthesis and decomposition experiment of mercury ash (HgO), and carried out a systematic study on it. It was found that it can synthesize various acids with many non-metallic elements, so it was named "acid gas" (in Greek).
Through the oxygen experiment, Lavoisier put forward the oxidation theory of combustion, overturned the phlogiston theory, launched the famous chemical revolution in the history of chemistry, and made the chemistry stand upright in the form of phlogiston theory in the past.Therefore, although he didn't find oxygen firstEngelsHe was still called "the man who really found oxygen", while Scheler and Priestley "didn't get the truth when the truth hit the tip of their nose".
In 1802, the German Oriental scholar Klaprault accidentally read a 64 page Chinese manuscript with the title《Ping Long Recognition》The author is Ma He, whose work was written in the first year of Zhide (756 AD) of the Tang Dynasty.After reading this book, Claptort was surprised to find that this book by a geomancer about how to find "dragon veins" on the earth revealed a profound scientific truth: oxygen exists in both air and water.
In 1807, Claptort read out a paper entitled "Chemical Knowledge of the Eighth Century Chinese" at the symposium of the Russian Academy of Sciences in Petersburg, which mentioned that there are "Yin and Yang" in the air, and "Yin" can be generated after heated by materials such as cinnabar and bluestone;There is also "Yin Qi" in the water, which is closely combined with "Yang Qi" and is difficult to decompose.Claptott pointed out that what Ma He called "Yin Qi" is oxygen.It proves that China knew the existence of oxygen as early as the Tang Dynasty and was able to decompose it, more than 1000 years before Europeans discovered oxygen.Claptott's paper surprised all the scientists present.[4]
Origin of name
Oxygen means "acid element" in Greek, which was named by French chemist Lavoisier because Lavoisier wrongly believed that all acids contain this new gas.The name of oxygen in Japanese is still "acid element".
The Chinese name of oxygen is Qing DynastyXu ShouNamed.He believed that human survival could not be separated from oxygen, so he named it "nourishing gas", that is, "the quality of nourishing gas". Later, in order to unify, he replaced the word "nourishing" with "oxygen", that is, "oxygen".
Experimentally, the paramagnetic resonance spectrum proves that O has paramagnetism, and also proves that O has two unpaired ground electrons.It shows that the original structure formula of oxygen molecule combined by double bond does not conform to the reality.
Structure of oxygen
The structure of oxygen is shown in the figure, ground state OtwoThere is no double bond in the molecule, but two three electron bonds are formed in the oxygen molecule.
Molecular Orbital Energy Level Diagram of Oxygen Molecule
The molecular orbital electron arrangement formula of oxygen is
, onπThere are unpaired single electrons in the orbit, so OtwoMolecule is the only one of all diatomic gas molecules that has even number of electrons and displaysParamagnetismSubstances.[5-6]
Sp orbitals of two oxygen atomsHybridization, a single electron is filled into the sp hybrid orbitalσBond, another single electron is filled into the p orbitalπKey.Oxygen isOdd electron molecule, withParamagnetism。[5]
Singlet oxygen and triplet oxygen
Ordinary oxygen contains two unpaired electrons, equivalent to a double radical.The two unpaired electrons have the same spin state,Spin quantum numberSum ofS=1，2S+1=3, soground stateOfOxygen moleculeThe spin multiplicity is 3, which is called triplet oxygen.[7]
Under excitation, two unpaired electrons of oxygen molecule pair, and the algebraic sum of spin quantum numbersS=0，2S+1=1, calledSinglet oxygen。
The oxygen in the air is mostly triplet oxygen.Ultraviolet radiation and someOrganic moleculeThe energy transfer to oxygen is the main reason for the formation of singlet oxygen.The oxidation capacity of singlet oxygen is higher than that of triplet oxygen.
one thousand one hundred and sixty-five point nine
chemical property
The chemical properties of oxygen are relatively active.exceptNoble gas, less activemetallic elementasgold、platinumIn addition to silver, most elements can react with oxygen. These reactions are called oxidation reactions, and the compounds produced by the reactions (consisting of two elements, one of which is oxygen) are calledoxide。In general,Nonmetallic oxideThe aqueous solution is acidic, while the alkaline metal or alkaline earth metal oxide is alkaline.In addition, almost all organic compounds can be violently burned in oxygen to produce carbon dioxide and water.Chemically, the chemical reaction between substances and oxygen was defined as oxidation reaction, and the oxidation-reduction reaction refers to the occurrence ofelectron transfer Or offset.Oxygen hasCombustibility，Oxidizability。[5]
Produce yellow flame, emit a lot of heat, and generate light yellow powder
Reaction with magnesium
Violent combustion emits dazzling strong light, emits a lot of heat, and generates white powdery solid.
Reaction with aluminum
Emit bright light, heat and white solid.
Reaction with iron
(Formation of rust)
The red hot wire burns violently, sparking all over the place, releasing a lot of heat and generating black solid.
The wire burns in a gas collector filled with oxygen
Reaction with zinc
Reaction with copper
After heating, a layer of black substance is formed on the bright red copper wire surface.
Reaction with nonmetals
Chemical equation
phenomenon
Reaction with hydrogen
It burns quietly, producing a light blue flame, generating water and releasing a lot of heat.[8]
Reaction with carbon
It burns violently, emits white light, emits heat, and generatesClarified lime waterTurbid gas.[9]
(When oxygen is insufficient)
Reaction with sulfur
Sulfur burns in oxygen
It burns in the air and emits a faint light blue flame;It burns more vigorously in pure oxygen, emits blue and purple flame, emits heat, and generates gas with pungent smell[10]。The gas can make the clarified lime water turbid, and can make the acid potassium permanganate solution orFuchsin solutionFading: The color of the faded magenta solution returns to red after heating.
White phosphorus spontaneously combusts in the air, emits light and heat, and generates white smoke.
Reaction with nitrogen
Reaction with organic matter
For example, methane, acetylene, alcohol, paraffin, etc. can be burned in oxygen to generate water and carbon dioxide.
The combustion of gaseous hydrocarbons usually emits a bright blue flame, giving off a lot of heat, generating water and gas that can make the clarified lime water turbid.
Heating potassium chlorate or potassium permanganate to produce oxygen[12]
1. Heating potassium permanganate:
The equation of thermal decomposition of potassium permanganate is controversial, because its decomposition products will be different under different temperature conditions
The air tightness shall be checked first in the experiment, and the tube shall be poured when heated evenly.
Collect the common drainage methods, remove the conduit first and then move the lamp.
Explanation:
1. The air tightness shall be checked first, and the test tube shall be tilted evenly when heated: "Test tube tilting" means that when installing a large test tube, the test tube shall be slightly tilted, that is, the test tube mouth shall be lower than the bottom of the test tube, so as to prevent a small amount of water contained in the drug from turning into steam when heated, and then freezing into water drops at the pipe mouth and flowing back, causing the test tube to break."Heating evenly" means that the test tube must be heated evenly when it is heated.
2. Common drainage method for collection: it means that oxygen shall be collected by drainage and gas collection method.
3. Withdraw the tube first and then move the lamp: This means that when oxygen production stops, the air duct must be removed from the water tank first, and then the alcohol lamp (if the alcohol lamp is removed first, the water will be sucked into the hot tube along the tube due to the temperature and pressure drop in the tube, causing the tube to break due to rapid cooling).
Pressurize at low temperature to change air into liquid and then evaporate. Since the boiling point of liquid nitrogen is - 196 ℃, which is lower than that of liquid oxygen (- 183 ℃)nitrogenFirst, it evaporates from liquid air, and the rest is mainly liquid oxygen.
The main components of air are oxygen and nitrogen.The method of air separation for preparing oxygen scale from air is based on the different boiling points of oxygen and nitrogen.First, precool and purify the air (remove a small amount of moisture, carbon dioxideacetylene、hydrocarbonAnd other impurities such as gas and dust), and then compressed and cooled to make it liquid air.Then, taking advantage of the different boiling points of oxygen and nitrogen, liquid air is evaporated and condensed for many times in the distillation tower to separate oxygen and nitrogen to obtain pure oxygen (up to 99.6% purity) and pure nitrogen (up to 99.9% purity).If some additional devices are added, rare inert gases such as argon, neon, helium, krypton, xenon, etc., which contain very little in the air, can also be extracted.The oxygen produced by the air separation device is compressed by the compressor, and then the compressed oxygen is stored in a high-pressure cylinder, or directly transported to the factory and workshop through pipes.Using this method to produce oxygen requires large complete sets of equipment and strict safe operation technology, but the output is high, thousands of cubic meters of oxygen can be produced per hour, and the raw materials used are only air that does not need to be bought, transported or stored in warehouses. Therefore, since the first cryogenic air separation oxygen generator was developed in 1903,This method of oxygen production has been the most widely used.
Membrane separation technology has developed rapidly.By using this technology, under a certain pressure, air can pass through the film with oxygen enrichment function to obtain oxygen enriched air with high oxygen content.Using this membrane for multistage separation, oxygen enriched air with more than 90% oxygen can be obtained.
Using the characteristic that nitrogen molecule is larger than oxygen molecule, special molecular sieve is used to separate oxygen from air.First, use the compressor to force the dry air through the molecular sieve into the vacuum absorber. The nitrogen molecules in the air are adsorbed by the molecular sieve, and the oxygen enters the absorber. When the oxygen in the absorber reaches a certain amount (pressure reaches a certain level), the oxygen outlet valve can be opened to release oxygen.After a period of time, the nitrogen adsorbed by the molecular sieve gradually increases, the adsorption capacity decreases, and the purity of the oxygen produced decreases. It is necessary to use a vacuum pump to extract the nitrogen adsorbed on the molecular sieve, and then repeat the above process.This method of producing oxygen is also called adsorption method.A small oxygen generator using adsorption method has been developed for home use.
4. Electrolytic oxygen production method
Put the water into the electrolytic cell, add sodium hydroxide or potassium hydroxide to improve the electrolysis degree of water, and then connect the direct current, the water will be decomposed into oxygen and hydrogen.For each cubic meter of oxygen produced, two cubic meters of hydrogen are obtained simultaneously.The electricity consumption for producing one cubic meter of oxygen by electrolysis is 12-15 kilowatt hours, which is very uneconomical compared with the power consumption of the above two methods (0.55-0.60 kilowatt hours).Therefore, electrolysis method is not suitable for large amount of oxygen production.In addition, if the hydrogen produced at the same time is not collected properly, it will gather in the air, such as mixing with oxygen, and will easily cause extremely violent explosion.Therefore, the electrolysis method is not applicable to the domestic oxygen production method.
Smelting process:When high-purity oxygen is blown in the steelmaking process, the oxygen will react with carbon and phosphorus, sulfur, silicon, etc., which not only reduces the carbon content of steel, but also helps to remove phosphorus, sulfur, silicon and other impurities.Moreover, the heat generated in the oxidation process is enough to maintain the temperature required for steelmaking. Therefore, oxygen blowing not only shortens the smelting time, but also improves the quality of steel.Blast furnace ironmakingIncreasing the oxygen concentration in the blast can reduce the coke ratio and increase the output.In nonferrous metal smeltingOxygen enrichmentIt can also shorten smelting time and increase output.
Chemical industry:In the production of synthetic ammonia, oxygen is mainly used for the oxidation of feed gas to strengthen the process and increase the yield of fertilizer.Another example is high temperature cracking of heavy oil and gasification of pulverized coal.
national defense industry:liquid oxygenIt is the best combustion supporting agent for modern rockets. In supersonic aircraft, liquid oxygen is also needed as an oxidant. Flammable materials impregnated with liquid oxygen have strong explosiveness and can be used to make liquid oxygen explosives.
Other aspects:It is used together with acetylene, propane and other combustible gases as a combustion supporting agent to achieve the role of welding and cutting metal. It is widely used in all walks of life, especially in machinery enterprises. It is also convenient for cutting. It is a preferred cutting method.
4. Subacute and chronic toxicity: under normal pressure, living in 80% oxygen for 4 days, rats began to die in succession, and rabbit optic cells were all damaged;In pure oxygen, rabbit 48 hOptic cellAll of them were damaged, dogs died within 60 hours, monkeys suffered from dyspnea within 3 days, and died within 6~9 days.[2]
5. Other toxic effects: TCLo: 100% (100%) (inhalation, 14h);TCLo: 80% (inhaled by rats).[2]
Negative effects of excessive oxygen inhalation:
Oxygen bottle
As early as the middle of the 19th century, British scientist Paul Burt first discovered that if animals breathe pure oxygen, they will be poisoned, and so will humans.If a person is exposed to pure oxygen greater than 0.05MPa (half atmospheric pressure), it is toxic to all cells. If he inhales it for a long time, "oxygen poisoning" may occur.The capillary barrier of the lung is destroyed, leading to pulmonary edema, pulmonary congestion and bleeding, which seriously affects the respiratory function, and then causes damage to various organs due to hypoxia.In a pure oxygen environment of 0.1MPa (1 atmosphere), people can only survive for 24 hours, and pneumonia will occur, eventually leading to respiratory failure and suffocation.People can stay for a maximum of 1.5 hours to 2 hours in the 0.2MPa (2 atmospheres) high-pressure pure oxygen environment, which will lead to brain poisoning, life rhythm disorder, mental disorder and memory loss.If 0.3MPa (3 atmospheres) or even higher oxygen is added, people will experience degeneration and necrosis of brain cells, convulsion and coma within a few minutes, leading to death.[17]
In addition, excessive oxygen intake can also promote life and aging.The oxygen entering the human body reacts with the oxidase in the cell to generatehydrogen peroxide, and then becomeLipofuscin。This lipofuscin is acceleratingCell senescenceIt accumulates in the heart muscle, aging the myocardial cells and reducing the heart function;It accumulates on the blood vessel wall, causing aging and hardening of blood vessels;It accumulates in the liver and weakens the liver function;Accumulation in the brain causes mental decline, memory decline, and people become dementia;It accumulates on the skin and forms age spots.
Effects of hypoxia and oxygen enrichment on human body
Fatal/4-5 minutes can be cured after treatment (absolute closed environment, such as hyperbaric oxygen chamber)
>23.5%
Oxygen enrichment
20.9%
Oxygen concentration is normal
19.5%
Minimum allowable oxygen concentration
15～19%
Reduces work efficiency and can cause problems in the head, lungs and circulatory system
10～12%
Shortness of breath, loss of judgment, purple lips
8～10%
Loss of intelligence, fainting, unconsciousness, pale face, purple lips, nausea and vomiting
6～8%
8 minutes
4～6%
Convulsions, respiratory arrest, death within 40 seconds
Poisoning or leakage treatment
First aid measures
Inhalation: quickly leave the site to a place with fresh air.Keep the respiratory tract unobstructed.If breathing stops, perform artificial respiration immediately.Get medical attention.
Extinguishing method: keep the container cool with water to prevent explosion caused by heat and rapid fire.Cut off the gas source quickly, spray water to protect the person who cut off the gas source, and then select appropriate extinguishing agent to extinguish the fire according to the cause of fire.[14]
On site treatment
Evacuate the personnel in the leakage contaminated area to the windward place quickly, isolate them, and strictly restrict access.Cut off the ignition source.It is recommended that emergency personnel wear self-contained positive pressure respirators and general work clothes.Avoid contact with combustibles or combustibles.Cut off the leakage source as much as possible.Reasonable ventilation to accelerate diffusion.Leaking containers shall be properly treated, repaired and inspected before reuse.[14]
Handling and storage
Operation precautions: closed operation.Closed operation, providing good natural ventilation conditions.Operators must be specially trained and strictly abide by the operating procedures.Keep away from kindling and heat sources, and smoking is strictly prohibited in the workplace.Keep away from flammable and combustible materials.Prevent gas leakage into the air of the workplace.Avoid contact with active metal powder.The cylinder and accessories shall be handled with care to prevent damage.Fire fighting equipment and leakage emergency treatment equipment of corresponding types and quantities shall be provided.[14]
Precautions for storage: store in a cool and ventilated warehouse.Keep away from kindling and heat sources.The warehouse temperature should not exceed 30 ℃.It shall be stored separately from combustible (combustible) materials, active metal powder, etc., and mixed storage is strictly prohibited.The storage area shall be equipped with leakage emergency treatment equipment.[14]
Individual protection
Engineering control: closed operation.Provide good natural ventilation conditions.
Body protection: wear general work clothes.
Hand protection: wear general operation protective gloves.
Other protection: Avoid high concentration inhalation.[14]
Storage and transportation method
Packing method: steel gas cylinder.
Transportation method: oxygen cylinders shall not be contaminated with grease.When steel cylinders are used for transportation, safety helmets on steel cylinders must be worn.Cylinders are generally placed horizontally, and the mouth of the cylinder should be in the same direction, not crossed;The height shall not exceed the protective fence of the vehicle, and shall be firmly clamped with triangular wood pad to prevent rolling.It is strictly prohibited to mix with combustibles or combustibles, active metal powder, etc.Transport in the morning and evening in summer to prevent sunlight exposure.It is forbidden to slip during railway transportation.[14]
The presence of oxygen
Announce
edit
The earth's atmosphere was oxygen free at the beginning of its formation.The original atmosphere is reductive, full of methane, ammonia and other gases.
The appearance of atmospheric oxygen comes from two kinds of actions, one is the photolysis of water with the participation of non living things, the other is the photosynthesis with the participation of living things.
Biological photosynthesis has a great impact on the atmosphere.It caused the atmosphere to change from reducing atmosphere to oxidizing atmosphere.The hydrogen generated by water photolysis can be oxidized back to the earth without spreading to outer space, thus preventing the loss of water on the earth.At the same time, photosynthesis has also accelerated the accumulation of atmospheric oxygen, profoundly changing the metabolic mode and body shape of species on the earth.The atmospheric oxygen content once rose to 35% in the Carboniferous.The increase of oxygen content resulted in the giant size of insects relying on osmotic oxygen delivery.In the Carboniferous, there was a giant dragonfly with a wingspan of 2.5 feet.[15]
New mechanism of origin
The research team of Professor Tian Shanxi of the University of Science and Technology of China found this "origin of oxygen", revealing a new mechanism for the generation of oxygen on the early Earth, indicating that oxygen does not come from photosynthesis.
In the early atmospheric environment, there were more carbon dioxide and low-energy electrons. Tian Shanxi's research team proposed that these carbon dioxide molecules could capture low-energy electrons and produce carbon atom negative ions and free oxygen atoms or oxygen molecules.The role of free oxygen atoms and oxygen molecules as products in early atmospheric chemical reactions was found through experiments.
Researchers found that the process of "low-energy electron attachment or capture" is crucial to the evolution of interstellar chemical composition.There are a lot of carbon dioxide gas and energy electrons in the sky of many planets (such as Earth, Mars, Saturn, etc.).The research team believes that the contribution of "electron attachment dissociation" to the origin of original oxygen may be more important than the previously recognized "three body composite reaction" and the newly discovered "photolysis reaction" process.This discovery has greatly deepened and expanded people's understanding of "interstellar medium chemical reactions".
