About Alkanes.doc - [edit Occurrence of alkanes in the Universe Methane and ethane make up a large proportion of Jupiter's atmosphere Alkanes form a

About Alkanes.doc - [edit Occurrence of alkanes in the...

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[ edit ] Occurrence of alkanes in the Universe Methane and ethane make up a large proportion of Jupiter's atmosphere Alkanes form a significant portion of the atmospheres of the outer gas planets such as Jupiter (0.1% methane, 0.0002% ethane), Saturn (0.2% methane, 0.0005% ethane), Uranus (1.99% methane, 0.00025% ethane) and Neptune (1.5% methane, 1.5 ppm ethane). Titan (1.6% methane), a satellite of Saturn, was examined by the Huygens probe which indicate that Titan's atmosphere periodically rains liquid methane onto the moon's surface. [4] Also on Titan, a methane-spewing volcano was spotted and this volcanism is believed to be a significant source of the methane in the atmosphere. There also appear to be Methane/Ethane lakes near the north polar regions of Titan, as discovered by Cassini's radar imaging. Methane and ethane have also been detected in the tail of the comet Hyakutake . Chemical analysis showed that the abundances of ethane and methane were roughly equal, which is thought to imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules. [5] . Alkanes have also been detected in meteorites such as carbonaceous chondrites . [ edit ] Occurrence of alkanes on Earth Traces of methane gas (about 0.0001% or 1 ppm) occur in the Earth's atmosphere, produced primarily by organisms such as Archaea , found for example in the gut of cows. [ citation needed ] Extraction of oil which containing many different hydrocarbons including alkanes
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The most important commercial sources for alkanes are natural gas and oil . [6] Natural gas contains primarily methane and ethane, with some propane and butane : oil is a mixture of liquid alkanes and other hydrocarbons . These hydrocarbons were formed when dead marine animals and plants (zooplankton and phytoplankton) died and sank to the bottom of ancient seas and were covered with sediments in an anoxic environment and converted over many millions of years at high temperatures and high pressure to their current form. Natural gas resulted thereby for example from the following reaction: C 6 H 12 O 6 → 3CH 4 + 3CO 2 These hydrocarbons collected in porous rocks, located beneath an impermeable cap rock and so are trapped. Unlike methane, which is constantly reformed in large quantities, higher alkanes (alkanes with 9 or more carbon atoms) rarely develop to a considerable extent in nature. [ citation needed ] These deposits e.g. ( oil fields ) have formed over millions of years and once exhausted can not be readily replaced. The depletion of these hydrocarbons is the basis for what is known as the energy crisis . The burning of these fossil fuels is the main source of global warming . [ citation needed ] Solid alkanes are known as tars and are formed when more volatile alkanes such as gases and oil evaporate from hydrocarbon deposits. One of the largest natural deposits of solid alkanes is in the asphalt lake known as the Pitch Lake in Trinidad and Tobago .
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