Nome: methane; methyl hydride; marsh gas
Registro CAS: 74-82-8
Massa Molar: 16.04246 g
Estados Físicos da Matéria: colorless gas
Percentagem de Massa: C 74.868 %; H 25.131 %
• "Used as a fuel and in the production of many organic compounds. Major component of natural gas. Formed by anaerobic decomposition of plants (swamp gas) and by microbes in termites and certain mammals. May contribute to global warming." 1
• "Carbon dioxide and water are not the only greenhouse gases. Methane, the CFCs, N2O, O3, and CO also absorb infrared radiation. Although they are present in the atmosphere at very low concentrations, they absorb infrared radiation relatively strongly and in regions of the spectrum not absorbed by CO2 and H2O." 2
• "When methane burns, it releases a large amount of energy, making it useful as a fuel. Humans have known about methane as a source of energy for thousands of years. Temples in the ancient world often burned "eternal flames" that may have been fueled by natural gas. In the early nineteenth century, people began using natural gas as a light source. Once oil was discovered in the 1860s, however, its use, and the electricity produced by burning oil, became much more popular, and people abandoned natural gas as a fuel except for limited use in cooking.
Natural gas has become more popular in recent years because its use results in less pollution that petroleum and other fossil fuels. Some uses include heating homes, offices, and factories; powering room heaters and air conditioners; and operating home appliances such as water heaters and stoves.
Scientists are now exploring other uses for methane and natural gas with the hope that they might eventually become the most important fuels used by humans. Methane has some advantages over petroleum and coal as a fuel. It burns more cleanly than either of these other fossil fuels, producing only carbon dioxide and water as combustion products. Some experts believe that methane could be used as a power source of fuel cells, cells that burn hydrogen to produce electricity. Adding natural gas to oil- or coal-fired burners would also help reduce the greenhouse gas emissions of these appliances.
In addition to its appliacations as a fuel, methane is used in the manufacture of a number of organic and inorganic compounds. For example, ammonia, which is then tenth most important chemical compound in the United States, based on quantity produced, is made from hydrogen and nitrogen gases. Over 90 percent of the hydrogen used to make ammonia is now obtained by reacting methane with water at high temperatures over a catalyst of iron oxide (Fe3O4). Other compounds produced from methane include methanol (methyl alcohol), acetylene (ethyne), formaldehyde (methanal), hydrogen cyanide, carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.
Methane is not toxic, but it can cause suffocation by reducing or eliminating the oxygen a person needs to breathe normally. The primary hazard posed by the gas is its flammability and explosive tendency." 5
Ponto de Fusão:*
-182.4°C 6 = 90.75 K = -296.32°F
Ponto de Ebulição:*
-161°C 7 = 112.15 K = -257.8°F
-161.5°C 6 = 111.65 K = -258.7°F
0.4228 at -162°C 6
* - 1 atm pressure
muito solúvel: benzeno 7
Ligações σ: 4
Ligações π: 0
Grupo Carboxila: 0
Ligações Químicas: polar covalent
Ionic Character: 10.61 %
CxHyOz + 0.25(4x+y-2z) O2 (g) → x CO2 (g) + 0.5y H2O (ℓ)
ΔHcomb° (g): -212.79 kcal = -890.31824 kJ
C (s graphite) + 2 H2 (g) → CH4 (g methane) 11
2 CH4 (g methane) + O2 (g) → 2 CO (g) + 4 H2 (g) 12
2 CH4 (g methane) + S8 (g) → 2 CS2 (g) + 4 H2S (g) 13
8 CH4 → C8H18 + 7 H2 14
CO (g) + 3 H2 (g) → CH4 (g) + H2O (g) 15
2 NH3 (g) + 3 O2 (g) + 2 CH4 (g) → 2 HCN (g) + 6 H2O (g) 16
2 NO (g) + 2 CH4 (g) → 2 HCN (g) + 2 H2O (g) + H2 (g) 17
CO2 (g) + H2 (g) → CH4 (g methane) + H2O (l) 18
NFPA 704 Ratings:
Health: 1 - Exposure would cause irritation with only minor residual injury.
Flammability: 4 - Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Includes pyrophoric substances. Flash point below 23°C (73°F).
Reactivity: 0 - Normally stable, even under fire exposure conditions, and is not reactive with water.
Catling, David C. and Zahnle, Kevin J. The Planetary Air Leak. Scientific American, May 2009, p 36-43. Matson, John. More Mysterious Methane. Scientific American, March 2009, p 21. Lorenz, Ralph and Sotin, Christophe. The Moon That Would be a Planet. Scientific American, March 2010, p 36-43. Cowen, Ron. Plumes of Martian Methane Hint at Possible Underground Microbial Life. Science News, February 14, 2009, p 10.
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