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Investigating the alcohols that use the most amount of energy to burn.

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Introduction

Investigating the alcohols that use the most amount of energy to burn Aim To find out which fuel uses the most amount of energy per mole Background Information We know already how atoms can 'exchange partners' in chemical reactions. This means that the bonds which join atoms to each other must be broken. However, new bonds have to be made as the product forms. Energy is needed to break bonds, it is like pulling 2 strong magnets apart, to pull the 2 magnets apart you require energy, therefore 'breaking bonds' requires energy and because it requires energy this means that it is endothermic. When you make new bonds it is the opposite of the above, it is like 2 magnets moving together because of the attraction, and because making bonds gives out energy it is exothermic. Bond Energy Bond energy is the amount of energy needed to break chemical bonds. We are able to calculate this energy from the table below, were we can see that particular bond require more energy than others to break. We can see from this table that bond energy is written in KJ/mol. ?H is also measured in KJ/mol. This unit stands for Kilojoules per mole and it is the energy needed to break a set number of bonds. ...read more.

Middle

= 20 * 4.2 * 16 = 1344J So amount of energy per gram = energy produced (J) / mass lost (g) =1344 / 1.5 = 896 J/g So amount of energy per mole = energy per gram * relative molecular mass = 896 * 74 = 66,304 J/mol or 66.304 KJ/mol Propanol Propanol energy produced = mass of water * 4.2 * ? = 20 * 4.2 * 19 = 1596J So amount of energy per gram = energy produced (J) / mass lost (g) =1596 / 1.5 = 1064 J/g So amount of energy per mole = energy per gram * relative molecular mass = 1064 * 60 = 63,840 J/mol or 63.840 KJ/mol Now that I have calculated the amount of energy used per mole I can draw up a final table of results that I can draw my graph from. Alcohol Mass (g) Time (m) Temperature Increase (c) Water Mass (cl) Mass at End (g) Energy used per mole (J/mol) Methanol 170.00 5.00 12 20 168.500 21.50 Ethanol 170.00 5.00 14 20 168.500 36.00 Butanol 170.00 5.00 16 20 168.500 66.30 Propanol 170.00 5.00 19 20 168.500 108.53 Prediction After analysing my preliminary results and my background information I think that the Butanol will give off the most energy per mole. ...read more.

Conclusion

/ 1.42 = 9464.78 J/g To calculate energy per mole we use energy per gram * relative molecular mass. Methanol = 4937 * 32 =136,320 J/mol Ethanol = 8093.75 * 46 =372,312.5 J/mol Butanol = 4937 * 74 =662,360.68 J/mol Propanol = 4937 * 60 =464545.2 J/mol Analysis From my graph I can see that Butanol (CH2 * 4) gives out the most amount of energy per mole. Butanol gives out the most amount of energy per mole because it has the most amount of atoms meaning a higher atomic mass. With a higher atomic mass we get higher bond energy, if there is high bond energy the alcohol is going to use a high amount of energy per mole. I know that because we are breaking bonds and we found that Butanol is giving out energy the process of breaking bonds is known as an exothermic reaction. Evaluation I think that this experiment could have been improved if we used more alcohols say something like 8 or 9 different alcohols to provide us with a larger scale of results, I think this would have improved the experiment because we would have had more results to analyse and conclude. A way in which this experiment could have been conducted better would be to have more accurate measuring facilities and a way in which we could more accurately calculate the energy per mole. ...read more.

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