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Investigating the combustion of varying alcohols.

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Introduction

Investigating the combustion of varying alcohols Aim To find the different rates for the combustion of alcohol. The aim is to find out how much energy is produced when burning these alcohols. Prediction As the alcohol burns, the temperature of the water will increase and the weight of the alcohol will decrease. This is due to evaporation that takes place because of the heat. Alcohols react with oxygen in the air to form water and carbon dioxide. The reaction that is involved in burning alcohols is exothermic because heat is given out. From this reason the reactant energy is higher than that of the product. I predict that the more bonds there are holding the carbon, oxygen and hydrogen atoms together; more energy will be required to break them apart. For example Ethanol has the formula C H OH. In this formula you have five C-H bonds, one C-C bond, one C-O bond and one O-H bond. To separate these types of bonds you require a certain amount of energy. Type of Bond Energy Required (joules) C-H 410 C-O 360 O-H 510 C-C 350 O=O 496 C=O 740 To separate C-H bond you need to apply 410 joules of energy. ...read more.

Middle

* Measure the temperature. * Re-weigh the alcohol and burner. * Calculate the difference. * Record the results. * Repeat these stages 2 times for each different alcohol. This will produce an average result. Results Ethanol Weight Before Weight After (g) Temp before Temp After (�C) 162.43 162.1 21 30 162.1 161.7 18 28 Ave. Weight Difference (g) Ave. Temp Difference (�C) 0.365 9.5 Propanol Weight Before Weight After (g) Temp before Temp After (�C) 189.11 188.7 20 25 188.7 188.3 19 27 Ave. Weight Difference (g) Ave. Temp Difference (�C) 0.405 6.5 Butanol Weight Before (g) Weight After Temp before (�C) Temp After (�C) 222.7 222.2 18.5 28.5 222.2 221.9 19 29 Ave. Weight Difference (g) Ave. Temp Difference (�C) 0.4 10 Pentanol Weight Before (g) Weight After (g) Temp before (�C) Temp After (�C) 215.2 214.8 18 32 214.8 214.45 19 32 Ave. Weight Difference (g) Ave. Temp Difference (�C) 0.375 13.5 Collected Results Alcohol Ave. Weight Difference Ave. Temp Difference Ethanol 0.365 9.5 Propanol 0.405 6.5 Butanol 0.4 10 Pentanol 0.375 13.5 Analysis The energy is given out when forming the bonds between the new water and carbon dioxide molecules. ...read more.

Conclusion

Somewhere in the experiment I must have slipped up because my results differ slightly to what I had hoped would happen. Alcohol Calculation Transfer by 1 gram of fuel Butanol 5670 60 94.5 Ethanol 4200 46 91.30 These two results didn't seem to fit with the others. Ethanol's transfer rate should have been higher than that of the Butanol. Overall I think my experiment was fairly accurate. However, I could have done certain things to make my results more accurate. Improving accuracy * I would have used a more accurate instrument to measure the temperature with, as this would have given me much better and more accurate results. * Also I would have used better equipment to reduce the heat loss in the experiment. Conclusion I have found that my prediction was correct. In my prediction I said that the amount of heat produced per gram would increase as the number of chemical bonds in an alcohol increases. This statement turned out to be true. So, I conclude that the most efficient alcohol out of the ones that I had investigated was Pentanol, and the least efficient was Ethanol. Sian Chesher Chemistry Coursework 5th February ...read more.

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