Ammonia and the Haber Process

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Ammonia and the Haber process Ammonia Ammonia (NH3) is a compound of nitrogen and hydrogen. It is a colourless gas with a choking smell, and a weak alkali which is very soluble in water. Ammonia is used to make fertilisers, explosives, dyes, household cleaners and nylon. It is also the most important raw material in the manufacture of nitric acid. Ammonia is manufactured by combining nitrogen and hydrogen in an important industrial process called the Haber process. An ammonia production plant. Photo courtesy of WMC Resources Ltd The Haber process The raw materials for this process are hydrogen and nitrogen. Hydrogen is obtained by reacting natural gas - methane - with steam, or through the cracking of oil. Nitrogen is obtained by burning hydrogen in air. Air is 80 per cent nitrogen; nearly all the rest is oxygen. When hydrogen is burned in air, the oxygen combines with the hydrogen, leaving nitrogen behind. Nitrogen and hydrogen will react together under these conditions: * a high temperature - about 450ºC * a high pressure - about 200 atmospheres (200 times normal pressure) * an iron catalyst The reaction is reversible. nitrogen + hydrogen ammonia N2(g) + 3H2(g) 2NH3(g) The (g) indicates that the substance is a gas. The flow chart shows the main stages in the Haber process. The reaction is reversible, and some nitrogen and hydrogen remain mixed with the ammonia. The reaction mixture is cooled so that the ammonia liquefies and can be removed. The remaining nitrogen and hydrogen are recycled. The Haber process for making

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