Properties of ammonia?

This post was last edited by adsl121 on 2010-3-9 at 12:52. It is a volatile gas that is soluble in water; its aqueous solution is weakly alkaline and reacts with acids. Covalent compounds. The accident at Sichuan Chemical Plant, in which ammonia polluted the Tuojiang River, was one of the top ten news stories across the country that year

This post was last edited by adsl121 on 2010-3-9 at 12:53. Physical properties: Hydrogen is a colorless gas with a density lower than that of air (it has the lowest density among all gases). Under standard conditions, the mass of 1 liter of hydrogen is 0.0899 grams; it is much lighter than air). Since hydrogen is insoluble in water, it can be collected using the displacement of water method. Furthermore, at a pressure of 101 kPa and a temperature of -252.87°C, hydrogen can be transformed into a colorless liquid ； -At 259.1°C, it turns into a snow-like solid. At room temperature, hydrogen has very stable properties and does not readily react with other substances. But when the conditions change (such as ignition, heating, the use of catalysts, etc.), the situation is different. Chemical properties of ammonia I. Molecular structure of ammonia Nitrogen atoms have 5 valence electrons, 3 of which are unpaired. When it combines with hydrogen atoms, each nitrogen atom can bond with 3 hydrogen atoms through polar covalent bonds to form an ammonia molecule; the nitrogen atom in the ammonia molecule also has a lone pair of electrons. The spatial structure of an ammonia molecule is triangular pyramidal, with three hydrogen atoms at the base of the pyramid and the nitrogen atom at the apex. The angle between every two N—H bonds is 107°18’, so the ammonia molecule is a polar molecule. II. Chemical properties of ammonia (1) Reaction with water: When ammonia dissolves in water, its molecules combine with water molecules through hydrogen bonds to form ammonium hydroxide (NH3•H2O). Ammonium hydroxide can partially ionize into ammonium ions and hydroxide ions; therefore, ammonia solution is weakly basic and can turn phenolphthalein solution red. The reaction of ammonia in water can be expressed as follows: Ammonium monohydrate is unstable and decomposes upon heating to yield ammonia and water. In ammonium hydroxide, there exist three species, three ions, and three equilibria: NH3, NH3•H2O, and H2O ； Ions: NH4+, OH-, H+ ； Three equilibria: NH3+H2O ⇌ NH3•H2O, NH4++OH- ⇌ H2O, H++OH-. Three applications of ammonia water in middle school chemistry experiments: ① Using a glass rod dipped in concentrated ammonia water to detect the presence of gases such as HCl ； ②In the laboratory, it is used to react with aluminum salt solutions to produce aluminum hydroxide ； ③Prepare a silver ammonia solution to test for the presence of aldehyde groups in organic molecules. (2) Reaction with acids: 2NH3 + H2SO4 ===(NH4)2SO4; 3NH3 + H3PO4 ===(NH4)3PO4; NH3 + CO2 + H2O === NH4HCO3. The essence of these reactions is that the lone pair of electrons on the nitrogen atom in ammonia bonds with hydrogen ions in the solution, which have empty orbitals, through coordinate bonds to form ionic crystals. If the reaction takes place in an aqueous solution, the ionic equation is: 8NH3 + 3Cl2 === N2 + 6NH4Cl (the yellow-green color disappears, and white smoke is produced). The actual reaction mechanism is: 2NH3 + 3Cl2 === N2 + 6HCl; NH3 + HCl === NH4Cl. The overall reaction equation is: 8NH3 + 3Cl2 === N2 + 6NH4Cl. There have been many accidents caused by ammonia leaks: at around 9:40 on August 5, 2009, at the Chifeng Pharmaceutical Factory in Hongshan District, Chifeng City, Inner Mongolia, a liquid ammonia transport truck leaked ammonia while delivering it to the factory’s workshops through pipelines. As a result of this ammonia leak in Chifeng, Inner Mongolia, 202 people needed medical treatment. http://news.qq.com/a/20090805/001750.htm On July 30, 2009, at 10:05, an ammonia leak occurred at a freezing plant in Lintou Village, Zhao’an County. http://press.idoican.com.cn/detail/articles/2009073146554/