QUESTION
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Distillation Boiling Points •increase with increasing number of carbons • more atoms, more electrons, more opportunities for induced dipole-induced dipole forces Heptane bp 98°C Octane bp 125°C Nonane bp 150°C Distillation © 2003 John Wiley and Sons Publishers Chapter 7: Petroleum Courtesy PhotoDisc, Inc. /Getty Images The Driving Force of Energy © 2003 John Wiley and Sons Publishers Courtesy Ken Karp Distilling pure water from strong tea. © 2003 John Wiley and Sons Publishers Figure 7.7: Distillations. Crude Oil • The differences in boiling points are used to separate hydrocarbons in crude oil. • Heating to higher temperatures produces gases that are removed and cooled. © 2003 John Wiley and Sons Publishers Figure 7.8: Schematic diagram of fractional distillation of crude oil. © 2003 John Wiley and Sons Publishers Courtesy Brett Frooner/The Image Bank/Getty Images A fractioning tower. Crude oil Naphtha (bp 95-150 °C) Kerosene (bp: 150-230 °C) C5-C12 Light gasoline (bp: 25-95 °C) C12-C15 Crude oil Gas oil (bp: 230-340 °C) Refinery gas C1-C4 C15-C25 Residue What is common between a Potato Canon and a Car http://auto.howstuffworks.com/engine2.htm Understanding the Cycles http://auto.howstuffworks.com/engine4.htm Figure 7.1: Schematic of a four-cylinder engine. © 2003 John Wiley and Sons Publishers http://www.keveney.com/otto.html Intake. During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a 'poppet' intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way, however most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring (not illustrated here). Compression. As the piston rises the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture. Power. At the top of the compression stroke the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward. Exhaust. At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder. © 2003 John Wiley and Sons Publishers Figure 7.2: (a) The beginning of the intake stroke. (b) The middle of the intake stroke. (c) The beginning of the compression stroke. (d) The beginning of the power stroke. (e) The beginning of the exhaust stroke. © 2003 John Wiley and Sons Publishers Figure 7.3: The compression ratio is volume A divided by volume B. © 2003 John Wiley and Sons Publishers Figure 7.4: Smooth ignition and knocking. © 2003 John Wiley and Sons Publishers Courtesy Tannen Mauryl/The Image Works Three grades of gasoline and their octane ratings. © 2003 John Wiley and Sons Publishers Figure 7.5: A combination of 2,2,4-trimethylpentane and heptane is used to evaluate octane ratings. © 2003 John Wiley and Sons Publishers Figure 7.6: Catalytic converter. © 2003 John Wiley and Sons Publishers Courtesy Seth Resnick/Liaison/Getty Images Removing old paint containing lead from the interior of a building. © 2003 John Wiley and Sons Publishers Courtesy Bill Grafton/The Reynolds Group. An MTBE warning label on a gasoline pump in California: “The state of California has determined that the use of this chemical presents a significant risk to the environment. © 2003 John Wiley and Sons Publishers Courtesy Tony Freeman/PhotoEdit Tank truck delivering gasoline to a gas station. © 2003 John Wiley and Sons Publishers Figure 7.5: A combination of 2,2,4-trimethylpentane and heptane is used to evaluate octane ratings. Petroleum Refining Reforming –increases branching of hydrocarbon chains branched hydrocarbons have better burning characteristics for automobile engines © 2003 John Wiley and Sons Publishers Figure 7.10: Isomerization of hexane to isohexane (2-methylpentane). © 2003 John Wiley and Sons Publishers Figure 7.11: Cyclization of hexane to cyclohexane. © 2003 John Wiley and Sons Publishers Figure 7.12: Aromatization of cyclohexane to benzene. Petroleum Refining •Cracking –converts high molecular weight hydrocarbons to more useful, low molecular weight ones © 2003 John Wiley and Sons Publishers Figure 7.9: Catalytic cracking. © 2003 John Wiley and Sons Publishers Courtesy Paul S. Howell/Liaison Agency, Inc./Getty Images Installing a tank of natural gas. © 2003 John Wiley and Sons Publishers Courtesy Vanessa Vick/Photo Researchers A bus powered by methanol. © 2003 John Wiley and Sons Publishers Courtesy PhotoDisc Inc./Getty Images Burning gasoline and other fossil fuels adds carbon dioxide to the atmosphere. © 2003 John Wiley and Sons Publishers Courtesy Michael George/Bruce Coleman, Inc. A greenhouse. © 2003 John Wiley and Sons Publishers Figure 8.7: The greenhouse effect. © 2003 John Wiley and Sons Publishers Figure 8.8: Planetary greenhouse effects. © 2003 John Wiley and Sons Publishers Courtesy Mark Marten/NASA/Science Source/Photo Researchers Courtesy NASA/Phototake Courtesy Philip & Karen Smith/Stone/Getty Images Landscapes of Venus, Earth, and Mars. © 2003 John Wiley and Sons Publishers Figure 8.9: Global temperature changes. © 2003 John Wiley and Sons Publishers Courtesy Peter Newton/Stone/Getty Images Will Alaska look like this as a result of the greenhouse effect? © 2003 John Wiley and Sons Publishers Courtesy Solectria Corporation An electric car. © 2003 John Wiley and Sons Publishers Courtesy PhotoDisc Inc./Getty Images Banks of wind turbines convert the energy of the wind into electricity. © 2003 John Wiley and Sons Publishers Figure 7.13: The essentials of a typical fuel cell. Chemistry of a Fuel Cell Anode side: 2H2 => 4H+ + 4eCathode side: O2 + 4H+ + 4e- => 2H2O Net reaction: 2H2 + O2 => 2H2O http://videos.howstuffworks.com/fuel-cell-video.htm •The anode, the negative terminal of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst. •The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water. •The electrolyte is the proton exchange membrane(PEM). This specially treated material, which looks something like ordinary kitchen plastic wrap, only conducts positively charged ions. The membrane blocks electrons. •The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the PEM. QUESTION © 2003 John Wiley and Sons Publishers What property of a liquid is characterized by its volatility? QUESTION © 2003 John Wiley and Sons Publishers During the operation of the four-stroke, internal combustion engine, which strokes (if any) are in operation under the following sets of conditions? (a) Both the intake valve and the exhaust valve are closed. (b) Only one of these valves is open. QUESTION © 2003 John Wiley and Sons Publishers What’s the difference between the “octane” that is given an octane rating of 100 and the octane of Table 7.3, with its rating of –20? QUESTION What is the molecular formula of tetraethyllead? © 2003 John Wiley and Sons Publishers QUESTION © 2003 John Wiley and Sons Publishers What automotive air pollutants are reduced by the use of catalytic converters? What pollutants are unaffected or perhaps increased? QUESTION © 2003 John Wiley and Sons Publishers Even if the internal combustion engine were so efficient in burning gasoline that no catalytic converters were needed to protect the environment, its likely that “leaded” gasoline would no longer be available. Why? QUESTION © 2003 John Wiley and Sons Publishers What facet of molecular structure other than the molecular weight or carbon content of its molecules affects the boiling point of an alkane? QUESTION © 2003 John Wiley and Sons Publishers Suppose that one product of cracking a C9 alkane is: CH3—CH2—CH2—CH2—CHCH2 What is the other hydrocarbon product? QUESTION © 2003 John Wiley and Sons Publishers Name two products produced by the isomerization of pentane. What is produced through the aromatization of cyclohexane?
