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Combustion of alcohols lab report

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Introduction

Aim: To calculate the enthalpy changes during the combustion of a variety of alcohols and to compare the results by calculating equimolar quantities. Apparatus and Materials: Safety glasses 8 spirit burners containing different alcohols A copper calorimeter Clamp and stand Thermometer (1?C) Weighing balance (0.01g) Method: 1. Weigh calorimeter 2. Reweigh calorimeter containing water (80 cm^3) 3. Place thermometer in water and note initial temperature 4. Weigh spirit burner with its cap. 5. Place the spirit burner under calorimeter (About 5cm) 6. Light the burner, stir the water with the thermometer (occasionally) and observe the rise in temperature. When it has risen between about 8 to 10?C, put the flame out with the cap, and measure more precisely the maximum temperature reached. 7. Weigh the burner and cap as soon as possible. 8. Repeat the experiment with all the other spirit burners (including unmarked one), changing the water each time. You do not need to reweigh the empty calorimeter, but you need to reweigh it with the water in it. Results: Table of Results Name of alcohol Weight of calorimeter with 80 cm^3 of water (g) ...read more.

Middle

Ethanol: 7952.37 for 0.32g ethanol Molar Mass = 46g 7952.37 x 46/0.32 = 1,143,153.19 J/Mol^-1 = 1,143.15 kJ/Mol^-1 Propanol: 8587.89 for 0.33g propanol Molar Mass = 60g 8587.89 x 60/0.33 = 1,561.43 Butanol: 7984.47 for 0.28g butanol Molar Mass = 74g 7984.47 x 74/0.28 = 2,110.18 Pentanol: 7991.49 for 0.32g pentanol Molar Mass = 88g 7991.49 x 88/0.32 = 2,197.66 Hexanol: 8605.83 for 0.32g hexanol Molar Mass = 102g 8605.83 x 102/0.32 = 2,743.11 Heptanol: 9908.48 for 0.38g heptanol Molar Mass = 116g 9908.48 x 116/0.38 = 3,024.69 Octanol: 11336.91 for 0.35g octanol Molar Mass = 130g 11336.91 x 130/0.35 = 4,210.85 Nonanol: 7341.63 for 0.19g Molar Mass = 144g 7341.63 x 144/0.19 = 5,564.18 Balanced equation for the combustion of ethanol C2H5OH(l ) + 302(g) --> 2C02(g) + 3H20(l ) Balanced equation for the combustion of propanol 2C3H7OH(l ) + 9O2(g) --> 6C02(g) + 8H20(l ) General equation for the combustion of alcohols Alcohol + Oxygen --> Carbon-Dioxide + Water CnH2n+1 + 02 --> C02 + H20 Conclusion and Evaluation According to my graph, the heat combustion increases as the molar mass increases, for both the literature values, and the values obtained from my experiment. ...read more.

Conclusion

Other weaknesses during this experiment could be the measuring of certain variables. The mass of the water inside the calorimeter might not have been 80 cm cubed, due to incorrect reading caused by the error parallax. Also, the flame was not always touching the calorimeter, so this would have caused differences in the amount of heat given off. Another weakness was that the amount of wick on the spirit burner was not the same on each burner, and the calorimeters had varying amounts of alcohol in them, so this would have caused differences in the amount of alcohol burnt. Lastly, although we used the digital thermometer, and were stirring the water to get the temperature, there would still be differences in the temperature of the water at different depths, and this would affect our results. In conclusion, to get slightly more accurate results, I would measure the wick length and height of calorimeter above the flame for each trial, I would make sure that each calorimeter has the same amount of alcohol in it, and I would also insulate the clamps and try other conductors to heat besides water. It might also help to take more readings so that the data is more consistent. Combustion of alcohols lab report 5/2/10 6:11 PM 5/2/10 6:11 PM 5/2/10 6:11 PM ...read more.

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