Molar Enthalpy of Combustion Using a Bomb Calorimeter Lab Report
A bomb calorimeter is a constant volume calorimeter that measures the heat released or absorbed and is applied to measure a given food’s or fuel’s calorie content. The apparatus has to withstand huge amounts of pressure in the process of measurement of the reaction. The energy supply used is electrical, and it facilitates the ignition and burning of the fuel. The escape of air is prevented to prevent the escape of heat from the apparatus. The change of water temperature, on the other hand, allows for the calculation of calorie content.
This is one of the most renowned methods of measuring energy transfer due to heat evolution in a chemical reaction and has become a feasible method for the determination of the unknown head of combustion of a given substance. This bomb calorimeter lab report experiment aimed to set up and verify the operation of an Adiabatic Bomb Calorimeter and determine the molar enthalpy of combustion of a given substance.
The researcher sought to measure and compare the molar enthalpy of combustion for Naphthalene and Benzoic acid with that estimated using just the mass of the bomb (5.76 kg) and the water (in manual) in the dewar flask.
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Determine the Calorimeter Constant for the Total Bomb Apparatus
Benzoic Acid mass = 0.300g = 0.016653 mol
=1.1K
The molar enthalpy of Naphthalene using the temperature rise measured in the calorimeter
The molar enthalpy of Benzoic acid using the temperature rise measured in the calorimeter
Compare the Molar Enthalpy of Combustion for Naphthalene and Benzoic Acid
Having calculated the molar enthalpy of combustion for Naphthalene and Benzoic acid with that estimated using just the mass of the bomb (5.76 kg) and the water in the dewar flask, it was found that 22,959.18kJ/mol was released in the case of Naphthalene and 35677.22kJ/mol in the case of Benzoic acid. The researcher noted that Benzoic acid, which has a molar mass of 122.12g/mol, had a bigger molar enthalpy than Naphthalene, which has a molar mass of 35677.22kJ/mol.
A Discussion of the Experiment
The bomb calorimeter facilitates the combustion of benzoic acid and Naphthalene in excess oxygen, thus making the heat of the apparatus. Benzoic acid is a colorless solid with the simplest aromatic carboxylic acid, carboxylic acid, with a molar mass of 122.12. The compound has a standard enthalpy of −385.2 kJ/mol formulation and a Standard enthalpy of combustion of −3228 kJ/mol. According to this experiment, 35677.22kJ of energy was released for every mole of the 0.3 grams of benzoic acid combusted. The former is the enthalpy content of one mole of the substance, while the latter is the heat value of the substance; thus, the amount of heat released when a given amount is burnt.
On the other hand, Naphthalene is an organic compound that has its simplest form as a white crystalline solid and tends to be fused by a pair of benzene rings. This compound has a standard enthalpy of 78.53 kJ/mol formulation and standard enthalpy of combustion of -5156.3 kJ/mol. After burring 0.3 grams of Naphthalene, 22,959.18kJ of energy for every mole of the compound burn. It was also noted that the compound with a larger mass had a relatively higher molar enthalpy. Therefore, it is clear that mass has a more significant effect on molar enthalpy than molar mass. The two compounds would have effectively determined the calorimeter constant (Shoemaker et al., 2003).
References:
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- P. W. Atkins, Physical Chmistry, 7th Ed, Oxford 2002.
- D. P. Shoemaker, C. W. Garland & J. W. Nibler, Experiments in Physical Chemistry, McGraw Hill, 2003.
