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Enthalpy of Combustion of Alchohols

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Introduction

Experiment 3: Enthalpy of Combustion of Alcohols ________________ Combustion of Ethanol Reaction: C2H5OH (l) + 3O2 (g) --> 2CO2 (g) + 3H2O (g) Raw Data Processed Data Mass of empty spirit lamp: 38.227 ± 0.001 grams Mass of ethanol: 54.408 – 38.227 = 16.181 ± 0.002 grams Mass of spirit lamp + ethanol: 54.408 ± 0.001 grams Mass of ethanol burnt: 54.408 – 51.283 = 3.125 ± 0.002 grams Final mass after burning: 51.283 ± 0.001 grams Rise in temperature: 40 – 27 = 13 ± 1°C Volume of water = 100 ± 0.5 ml Mass of water: 100 x 1 = 100 grams Initial Temperature = 27 ± ...read more.

Middle

80 kJ mol-1 Error Propagations Uncertainty in mass: Uncertainty in measuring cylinder: Uncertainty in temperature: Total uncertainty: 0.064 + 7.69 + 0.5 = 8.254% Uncertainty in enthalpy value: 8.254% of 80 kJ/mol = ± 6.6032 kJ/mol The percentage error compared to literature value: ïThe standard enthalpy change of combustion of ethanol (with uncertainty) is: -80 ± 6.6032 kJ mol-1 Combustion of Methanol Reaction: 2CH3OH (l) + 3O2 (g) --> 2CO2 (g) + 4H2O (g) Raw Data Processed Data Mass of empty spirit lamp: 36.113 ± 0.001 grams Mass of methanol: 52.435 – 36.113= 16.322 ± 0.002 grams Mass of spirit lamp + ethanol: 52.435 ± 0.001 grams Mass of methanol ...read more.

Conclusion

use this equation: Energy = 4.18 x 100 x 20 = 8360 Joules Mass of ethanol ÷ Molar mass of ethanol ï 5.17 g ÷ 46.06844 g/mol ï 0.11222 moles Assuming that all the heat is transferred to water, the calculated enthalpy of combustion of ethanol is: = 74,496.52468 Joules/mol ï 74.5 kJ mol-1 Error Propagations Uncertainty in mass: Uncertainty in measuring cylinder: Uncertainty in temperature: Total uncertainty: 0.0387 + 5 + 0.5 = 5.5387% Uncertainty in enthalpy value: 5.5387% of 74.5 kJ/mol = ± 4.13 kJ/mol The percentage error compared to literature value: ïThe standard enthalpy change of combustion of methanol (with uncertainty) is: -74.5 ± 7.413 kJ mol-1 ...read more.

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