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Energy Released From the Complete Combustion of Different Alcohols

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Introduction

Name : Youhanna Andraws Kamal El Alfy Class : 4/6 Activity : C5.01-05 Dated : 10-3-2004 Coursework Assignment Energy Released From the Complete Combustion of Different Alcohols Energy Released From the Complete Combustion of Different Alcohols I. (PLANNING) 1-The Aim of work: A fuel is a substance which can be conveniently used as a cheap source of energy. In this experiment the key factor that I plan to investigate is the amount of energy released from burning different fuels. I will be burning five different alcohols, ethanol, methanol, propanol, pentanol and butanol. My aim is to find the energy produced from burning of each one of these alcohols and afterwards calculate the heat value for each. This energy is given out when forming bonds between the new water and the carbon dioxide molecules I have used water since it is safe, abundant and has a specific heat capacity which is 4.18. In a chemical reaction bonds between atoms in the reactant molecules are broken and new bonds are formed in the products. Burning fuels is an exothermic reaction, because there is heat released and the total energy released in bond formation is greater than that energy needed for bond breaking. 2- Equations: CH3OH + 2 O2 CO2 + 2 H2O Methanol C2H5OH + 3 O2 2 CO2 + 3 H2O Ethanol 2 C3H7OH + 9 O2 6 CO2 + 8 H2O Propanol C4H9OH + 6 O2 4 CO2 + 5 H2O Butanol 2 C5H11OH + 17 O2 10 CO2 + 12 ...read more.

Middle

* Clean the can from outside by water each time after utilization. 10- Resources: ? http://www.essaybank.co.uk/GCSE/chemistry-course work ? http://www.edexcel.org.uk ? Earl Band Wilford LDR: chemistry 2nd edition. ? GCSE in a week: with Dan Evans and Alex Watts. ? GCSE success: with Emma Poole. II. (OBTAINING EVIDENCE) 1. Results: a) With Ethanol: 1- The mass of spirit burner before heating = 233.07g 2- The mass of empty can = 31.78g 3- The mass of can with water = 230.05g 4- The mass of water = 194.03g 5- The initial temperature of water = 18.0�C 6- The temperature of water after heating = 75.0 �C 7- The mass of spirit burner after heating = 225.81g Heat given by fuel = Heat absorbed by water Moles x ?H = M x C x ?? X ?H = M x 4.18 x (t2-t1) ?H Ethanol = = - 292.914 kJ/mol b) With Propanol: 1- The mass of spirit burner before heating = 253.43g 2- The mass of empty can = 30.51g 3- The mass of can with water = 220.33g 4- The mass of water = 189.76g 5- The initial temperature of water = 18.0�C 6- The temperature of water after heating = 75.0 �C 7- The mass of spirit burner after heating = 249.65 g Heat given by fuel = Heat absorbed by water Moles x ?H = M x C x ?? X ?H = M x 4.18 x (t2-t1) ...read more.

Conclusion

I suggest that maybe the temperature of the lab had slightly changed, but I am sure that I have accidentally dropped some ethanol during out the experiment. I have found from the graph that the theoretical results are much bigger on the graph from the practical results. I suggest the following sources of error for this great difference between the practical results and the theoretical results: * There is some alcohol evaporating from the spirit burner without complete combustion. * There is some carbon in the form soot on the walls of the can which indicates the incomplete combustion of the fuel. * The spirit burner itself, the metal can and the thermometer absorb some heat. * There is heat lost by radiation and convection. * May the water has boiled, leading to energy consumption without no further rise in temperature. * The thermometer might had touched the bottom of the metal can giving a false reading. 2- Improvements: I suggest using a heat insulator to prevent any heat loss by radiation. May be increasing the number of used alcohols may improve to the quality of the evidence. In addition, I suggest using an air tight to prevent any alcohol from evaporating out of the spirit burner and supplying enough oxygen for the complete combustion of the fuel. 3- Further work: I am going to repeat the experiment for the alcohol ethanol three times and get an average to get accurate and precise results. ...read more.

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