Resonance Energy of Naphthalene by Bomb Calorimetry
Experiment 3: Resonance Energy of Naphthalene by Bomb Calorimetry
Cameron Fowler
CHEM 457: Lab Section 4
Submitted: 11/4/10
Lab Group #3:
Michael Hyle
Neil Baranik
Tim Riley
Abstract:
The enthalpy of combustion of naphthalene was experimentally determined to be -5030.44 ± 78.98 kJ/mol which was a 2.5% error from the literature value of -5160 ± 20 kJ/mol.2 The theoretical enthalpy of combustion of solid naphthalene was calculated to be -6862.68 kJ/mol using bond energies for the gaseous molecules, the heat of vaporization of liquid water and the literature value of the heat of sublimation of naphthalene, which was 72 ± 4 kJ/mol.2 The absolute value of the difference between the theoretical heat of combustion and the literature value heat of combustion of naphthalene was 1702.68 ± 20 kJ/mol.2 This difference indicates that the resonance energy of naphthalene is very high and that its most stable configuration has a much lower energy than the unstable configuration that was combusted during this experiment. The results were obtained using bomb calorimetry where a sample was combusted in a bomb immersed in water, and the variations in water temperature were used to determine the heat of the combustion.
Introduction:
The resonance energy of a molecule is the difference in energy between the actual configuration of a molecule and that molecule’s most stable structure. It is useful to know the resonance energy of a species as it describes the difference between an experimentally determined heat of combustion and a theoretical one, calculated using bond energies with Hess’s Law.1 This comparison gives insight into how stable the molecules being combusted in the experiment are, as well as how the environment in which they were combusted differs from standard pressure and temperature. There were three distinct goals that were to be accomplished during this experiment. An experimental enthalpy of combustion of naphthalene was to be calculated and
Cameron Fowler
CHEM 457: Lab Section 4
Submitted: 11/4/10
Lab Group #3:
Michael Hyle
Neil Baranik
Tim Riley
Abstract:
The enthalpy of combustion of naphthalene was experimentally determined to be -5030.44 ± 78.98 kJ/mol which was a 2.5% error from the literature value of -5160 ± 20 kJ/mol.2 The theoretical enthalpy of combustion of solid naphthalene was calculated to be -6862.68 kJ/mol using bond energies for the gaseous molecules, the heat of vaporization of liquid water and the literature value of the heat of sublimation of naphthalene, which was 72 ± 4 kJ/mol.2 The absolute value of the difference between the theoretical heat of combustion and the literature value heat of combustion of naphthalene was 1702.68 ± 20 kJ/mol.2 This difference indicates that the resonance energy of naphthalene is very high and that its most stable configuration has a much lower energy than the unstable configuration that was combusted during this experiment. The results were obtained using bomb calorimetry where a sample was combusted in a bomb immersed in water, and the variations in water temperature were used to determine the heat of the combustion.
Introduction:
The resonance energy of a molecule is the difference in energy between the actual configuration of a molecule and that molecule’s most stable structure. It is useful to know the resonance energy of a species as it describes the difference between an experimentally determined heat of combustion and a theoretical one, calculated using bond energies with Hess’s Law.1 This comparison gives insight into how stable the molecules being combusted in the experiment are, as well as how the environment in which they were combusted differs from standard pressure and temperature. There were three distinct goals that were to be accomplished during this experiment. An experimental enthalpy of combustion of naphthalene was to be calculated and
References: (3) McMurry, J. Organic Chemistry, 5th ed., Brooks/Cole Publishing Co.: CA, 2000, p. 564-566.