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AND COMPOUNDS OF CARBON (Назад на главную)Organic chemistry is an extremely interesting field of natural science and of great technological significance. The overwhelming majority of chemists prove to be engaged in producing organic compounds; several millions being known so far. In view of their obvious success in the manufacture of synthetic compounds, the chemists are greatly interested in this field of science. The name organic chemistry, which was originally used to refer to the chemistry of substances that occur in living organisms, is now used for the chemistry of the compounds of carbon. The chemistry of carbon was greatly advanced about a century ago through the development of a general structure theory, this theory being a chemical theory, induced from chemical facts. In recent years it has received added verification through the determination of exact structures of molecules and crystals by physical methods, especially X-ray diffraction, electron diffraction, and the analysis of the spectra of substances. During the first half of the 19th century many organic compounds were found to have been obtained from plants and animals and also to have been made in the laboratory. The were analyzed for their constituent elements, an their properties were carefully studied. Efforts were made to find some correlation between the chemical composition and the properties of the substances. Elementary Carbon.Carbon occurs in nature in its elementary state in two allotropic forms namely diamond, this being the hardest substance known, and graphite, a soft, black crystalline substance used as a lubricant. Having investigated all the substances thoroughly the scientists found charcoal, coke, and carbon black; to be microcrystalline or amorphous (noncrystalline) forms of carbon. Carbon burns to form gases: carbon monoxide CO, and carbon dioxide CO2, the former being produced when there is a deficiency of oxygen or the flame temperature is very high. This investigation followed by others resulted in new discoveries in the field of carbon. It has been found out that carbon monoxide is a colourless, odourless gas with small solubility in water. It is poisonous, because of its ability to combine with the hemoglobin in the blood in the same way that oxygen does, and thus to prevent the hemolobin from combining with oxygen in the lungs and carrying it to the tissues. It should be noted that the exhaust as from automobile engines contains some carbon. Nevertheless carbon monoxide is a valuable industrial gas, for use as a fuel and as a reducing agent. Carbon Dioxide.Carbon dioxide is a colourless, odourless gas with a weakly acid taste, due to the formation of some carbonic acid when it is dissolved in water. It appears to be about 50'/o heavier than air. It is easily soluble in water, one liter of water at O'C dissolving 1,713 ml of the gas under 1 atm pressure. When crystalline carbon dioxide is heated from a very low temperature its vapour pressure reaches 1 atm at 79' at which temperature it vaporizes without melting. If pressure were increased to 2.5 atm the crystalline substance would melt to a liquid at 56.6'. Under ordinary pressure, then, the solid substance could be changed directly to a gas. Carbon dioxide is known to combine with water to form carbonic acid H2CO3 , it being a weak acid. If you studied all the properties more thoroughly you would see that carbon dioxide is used for the manufacture of sodium carbonate, sodium hydrogen carbonate, and carbonated water and for many other uses. From this short review it's clear that chemistry of carbon and its compounds is a very important field of chemistry and should be studied carefully. II Carbon PollutantsCarbon monoxide and carbon dioxide are both very important atmospheric contaminants. Human activities are responsible for the introduction of increasing quantities of these gases to the atmosphere. Carbon monoxide is particularly important because of its potent mammalian toxicity, while carbon dioxide is most significant because of its ability to regulate global temperature. Neither gas is tought to causedirect damage to vegetation at ambient concentrations presently monitored. Carbon monoxide has not been shown to produce acute effects on plants at concentrations below 100 p.p.m. for exposures from one to three weeks. The threshold of carbon dioxide toxicity to plants is in such excess of ambient conditions as to be completely unimportant. The hypothesis that the increasing concentration of carbon dioxide in the atmosphere might result in elevated global temperatures, however, has enormous implications for the health of forest ecosystems. Notes to the text: 1. overwhelming 2. majority 3. to be engaged 4. so far 6. in view of 7. recent 8. verification 9. correlation 10. lubricant 11. carbon 12. poisonous 13. exhaust gas 14. valuable 15. to reduce 16. to damage 17. to prevent 18. to be responsible for
I. Answer the following questions: 1. What is organic chemistry. 2. Why are the scientists interested in the field of organic chemistry. 3. What does the name organic chemistry refer to? 4. When was the chemistry of carbon advanced'? 5. What phenomenon was found during the first half of the 19th century. 6. Where does carbon occur? 7. In that form does carbon occur in nature? 8. What gases does carbon form during its burning? 9. What properties of ca-bon monoxide do you know? 10. What properties of carbon dioxide do you know'? l l. What does carbon dioxide form combining with water? 12. What are very important atmospheric contaminants? II. Retell the text according to the following plan: 1. Organic chemistry. 2. The chemistry of carbon. 3. Elementary carbon, 4. The properties of carbon. 5. Carbon monoxide. 6. Carbon dioxide. 7. Carbon pollutants. Date: 2015-12-17; view: 2278
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