Air is a Mixture:
The air around us is a mixture of gases, mainly nitrogen and oxygen, but containing much smaller amounts of water vapor, argon, and carbon dioxide, and very small amounts of other gases. Air also contains suspended dust, spores, and bacteria. Because of the action of wind, the percent composition of air varies only slightly with altitude and location.watch Air is a Mixture to learn more.
The amount of water in the air varies tremendously with location, temperature, and time. In deserts and at low temperatures, the content of water vapor can be less than 0.1% by volume. In warm, humid zones, the air may contain over 6% water vapor. Air is the commercial source for many of the gases it contains. It is separated into its components by fractional distillation of liquefied air. Before air is liquefied, water vapor and carbon dioxide are removed, because these substances solidify when cooled and would clog the pipes of the air liquefaction plant. The dry, CO2-free air is compressed to about 200 atmospheres. This compression causes the air to become warm, and the heat is removed by passing the compressed air through radiators. The cooled, compressed air is then allowed to expand rapidly. The rapid expansion causes the air to become cold, so cold that some of it condenses. By the alternate compressing and expanding of air, most of it can be liquefied. Nitrogen is obtained from liquid air by distillation at -196EC. The gas obtained by this process is actually a mixture of nitrogen and about 1.25% noble (or “inert”) gases, argon, neon, krypton, and xenon. Nitrogen is second only to sulfuric acid in the volume produced by the U.S. chemical industry. Its major uses are as an inert blanketing atmosphere in chemical processing (14%), electronics (15%), and, in liquid form, as a freezing agent (21%). Nitrogen is used to make agricultural fertilizers, such as ammonia and nitrates. It is also used in the production of acrylonitrile, CH2=CHCN, which is important in the manufacture of synthetic fibers such as Orlon, and in the production of cyanamide, HN=C=NH, which is polymerized to Melamine plastic. Because it is a very poor oxidizing agent, nitrogen is used to pack oxidizable foods, such as ground coffee, and as an inert atmosphere in the manufacture of electronic components. Liquefied nitrogen, because it is very cold, is used extensively to chill materials for preservation, as in freeze-drying of foods, and in manufacturing processes that require low temperatures, such as machining of aluminum.
Useful for CBSE, ICSE, NCERT & International Students
Grade : 8
Subject : Chemistry
Lesson : Air
Topic: Air is a Mixture
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