The Combustion of Alcohols
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Ryan McCarley GCSE Chemistry Coursework The Combustion of Alcohols Aim) My aim in this is experiment is to see how good a fuel alcohol is. Background Knowledge) Combustion is the rapid chemical reaction between substances that is usually accompanied by generation of heat and light in the form of flame. In most cases, oxygen comprises one of the reactants. Other physical phenomena that sometimes occur during combustion reactions are explosion and detonation. Combustion, one of the most important classes of chemical reaction, is often considered a climax phenomenon in the oxidation of certain types of substances. Although most flames have regions where reduction reactions are important, combustion is primarily the combining of combustible material with oxygen. Chemical and physical aspects) The chemical processes in combustion are most commonly initiated by such factors as heat, light, and sparks. As the combustible materials achieve the ignition temperature specific to the materials and the ambient pressure, the combustion reaction begins. The combustion spreads from the ignition source to the adjacent layer of gas mixture; in turn, each point of the burning layer serves as an ignition source for the next adjacent layer, and so on. Combustion terminates when equilibrium is achieved between the total heat energies of the reactants and the total heat energies of the products. Combustion may be propagated by complicated branched-chain reactions, as in hydrogen combustion. Other types of reactions, such as the combustion of carbon monoxide, are characterized by a fast interaction step between a hydroxyl radical (OH) and the carbon monoxide molecule (CO). Although the mechanisms of hydrocarbon combustion are not completely known, many of the steps involving hydrogen and oxygen atoms and hydroxyl and organic radicals are similar to those for hydrogen and carbon monoxide combustion. In addition to the chemical processes in combustion, physical processes that transfer mass and energy also occur. In gaseous combustion, for example, the diffusion of reactants and combustion products depends on their concentrations, pressure and temperature changes, and diffusion coefficients.
+360 +463 + (4.5 x 496) = 6633 kJ/ mol (6 x 743) + (8 x 463) = 8162 kJ/ mol 6633 - 8162 = -1529 =-1529 kJ/ mol * Propan-2-ol: (7 x 412) +(2 x 347) +360 +463 + (4.5 x 496) = 6633 kJ/ mol (6 x 743) + (8 x 463) = 8162 kJ/ mol 6633 - 8162 = -1529 =-1529 kJ/ mol * Butan-1-ol: (9 x 412) +(3 x 347) +360 + 463 + (6 x 496) = 8548 kJ/ mol (8 x 743) + (10 x 463) = 10,574 kJ/ mol 8548-10,574 = -2026 =-2026 kJ/ mol * Fuel Amount of energy given off Methanol -535 kJ/ mol * Ethanol -1032 kJ/ mol * Propan-1-ol -1529 kJ/ mol * Propan-2-ol -1529 kJ/ mol * Butan-1-ol -2026 kJ/ mol * Note: *- the minus means the reaction is exothermic. As you can see from my results, my prediction is proven as Butan-1ol is the biggest alcohol and I predicted that it would give of the biggest amount of energy. This is shown were it gives off -2026 kJ/ mol compared to the others where not as much energy is given off. Method) Equipment List) ? 5 Fuel Burners containing the different named Alcohols. ? 1 Boiling Tube. ? 1 Thermometer. ? 1 Clamp and Stand. ? 1 Measuring Cylinder. ? 1 Electronic Weighing Scales. ? 450cm3 of Water. Safety) ? The alcohols we are using are all flammable and so take great care when carrying them around. Make sure any spills of alcohol are cleaned up quickly. ? Make sure you wear goggles at all times, as there is a naked flame being used and an alcohol is being burned so goggles are essential. ? Make sure that when carrying the burner you do so from the bottom where the temperature is low and so there is no risk of dropping the burner.
These changes would, in my opinion give us more satisfactory results and practical ? Hs that were a lot closer to the theoretical ? Hs. I believe that realistically this was not a real fair test and this was due to all of the surroundings and the amount of heat lost to them. The flame of each burner was a naked flame and it was in open air, which would and did affect the experiment greatly. Extra Information) I could get extra information for this experiment by carrying out more preliminary tests or looking up from books and encyclopaedias. Another major source of information that could be useful in my investigation is the Internet. This extra work could help me to predict much more precisely and of greater accuracy. It would also give me more background information and hopefully help me to understand and grasp the concepts of fuels, combustion and other related topics. I believe that a major aspect of receiving greater information of 'The Combustion of Fuels' would be to take this experiment to another step and use a greater amount of fuels, for example: ? Pentanol ? Hexanol ? Heptanol Etc. However, even though I would find new topics and related subjects to my investigation, I would also find a great amount of the same as to what I already have obtained as many sources contain the same work. ________________________________________ Butan-1-ol Propan-2-ol Propan-1-ol Ethanol Methanol Fuel 192.55 192.38 192.21 197.91 198.88 198.30 134.84 134.57 134.29 189.81 189.52 189.17 145.71 145.25 140.03 1) 2) 3) Mass Before (g) 192.38 192.21 192.03 197.56 198.57 197.98 134.59 134.31 134.03 189.54 189.20 188.87 145.28 144.83 139.55 1) 2) 3) Mass After (g) 0.17 0.17 0.18 0.34 0.31 0.32 0.25 0.26 0.26 0.27 0.32 0.30 0.43 0.42 0.48 1) 2) 3) Mass Change (g) 0.17 g 0.32 g 0.26 g 0.30 g 0.44 g Average Mass Change (g) http://www.coursework.info/ This document was downloaded from Coursework.Info - The UK's Coursework Database Click here to visit Coursework.Info/
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