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Subject - Inorganic Chemistry

Carbon dioxide is a chemical compound containing carbon and oxygen, having the formula CO2 and the molar mass of 44.01 gmol-1 . Carbon dioxide is an odorless and non-flammable gas which is heavier than air. Under reduced pressure, the gas liquifies. Because of rapid evaporation of part of the liquid, the remaining part cools down to approximately 80°C and solidifies. The resulting "carbon dioxide snow" is used as fire extinguishing agent and as refrigerant (dry ice). Health wise, carbon dioxide is safe and is used as an inert gas in propellants and for the protection of food. Carbon dioxide is very soluble in water, however, only 0.1% of the dissolved molecules react with water to give carbonic acid. Therefore, carbon dioxide is the anhydride of carbonic acid. In nature, free carbon dioxide occurs in Earth's atmosphere, in mineral springs and in the ocean; in a bound state it is found in carbonates. In the laboratory, carbon dioxide is generated by reacting carbonates, e.g. marble (calcium carbonate), CaCO3 with hydrochloric acid using the Kipp's apparatus

CaCO3+2HClCaCl2+H2O+CO2

In industry, carbon dioxide is generated in many large-scale processes, for example, during the burning of coke with air or as a side product in lime burning (calcination of limestone). Carbon dioxide is an essential part of the metabolic system in flora and fauna (photosynthesis, respiration). In addition to other gases, it mainly is carbon dioxide that absorbs the heat radiating from Earth's surface and contributes to its warming (greenhouse effect). The increased concentration of carbon dioxide in Earth's atmosphere, generated by the ever larger output from industrial nations, is the main reason of an increase in average temperatures which has been observed for decades. The results are global climate changes, the outcome of which are hard to predict and which might have irreversible effects on man and nature.

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