Bomb Calorimetry
The goal of this experiment is to determine the enthalpy of combustion of naphthalene by means of a bomb calorimeter. First, the bomb calorimeter was standardized using benzoic acid and the average heat capacity of the bomb calorimeter was calculated to be 10.60.3205 kJ/K. From that, the
These results show that heats of combustions of unknown substances can be determined via bomb calorimetry.
Introduction
The first law of thermodynamics states that energy is conserved.2 Using that law it can be said that the change in the internal energy of a system () depends on the heat added (q) to the system and the work (w) done by the system.2 Equation 1 illustrates the relationship between the three variables. (1)
In this experiment, …show more content…
The remnants of the ignition wire were weighed at the end of each run. Before the start of the experiment and in between each run, the bomb and pan was wiped down to remove any remains of the substances. The pail was also refilled with 2L of distilled water. Each pellet was made before the start of its run to decrease the amount of water vapor in the air that could get inside of it.
Using the data obtained from the experiment a plot of time vs temperature was made and used to calculate the adiabatic temperature change. These plots can be seen in the appendix along with the equation of the trend lines. Equation 9 is used as well to calculate the adiabatic temperature change. However, equation 9 can be simplified to 10 because by inspection of figures 4 and 5 the slope of the line is small or simply 0. This slope corresponds to (dT/dt) in equation 9. Therefore, it is negligible. T= (Tf-Ti) – () (td-ti)- ()f (tf -td) …show more content…
Equation 11 is used to find the heat released in combustion of naphthalene or the energy of combustion (ΔE). qcomb= ΔUcomb*(mBA) + ΔUwire*(mwire) (11)
ΔUcomb and ΔUwire are the specific energies of benzoic acid and the iron fuse wire. They correspond to the values -26.41 kJ/g for benzoic acid and -6.68 kJ/g for iron.1 The change in temperature is assumed to be entirely from the result of the combustion of a substance and not from heat from the universe, i.e. this part of the apparatus is adiabatic (quniv=0). This is assumption is displayed in equation 12. qcal is the heat absorbed by the calorimeter. qcomb + qcal= quniv qconb = -qcal (12)
In order to use equation 13 it is also assumed that the temperature change of the water is the temperature change in the bomb calorimeter. The heat capacity of the bomb calorimeter (CVcal) was found to be 10.9kJ/K for the first trial of benzoic acid and 10.4kJ/K for the second trial. This gives a mean of
These results show that heats of combustions of unknown substances can be determined via bomb calorimetry.
Introduction
The first law of thermodynamics states that energy is conserved.2 Using that law it can be said that the change in the internal energy of a system () depends on the heat added (q) to the system and the work (w) done by the system.2 Equation 1 illustrates the relationship between the three variables. (1)
In this experiment, …show more content…
The remnants of the ignition wire were weighed at the end of each run. Before the start of the experiment and in between each run, the bomb and pan was wiped down to remove any remains of the substances. The pail was also refilled with 2L of distilled water. Each pellet was made before the start of its run to decrease the amount of water vapor in the air that could get inside of it.
Using the data obtained from the experiment a plot of time vs temperature was made and used to calculate the adiabatic temperature change. These plots can be seen in the appendix along with the equation of the trend lines. Equation 9 is used as well to calculate the adiabatic temperature change. However, equation 9 can be simplified to 10 because by inspection of figures 4 and 5 the slope of the line is small or simply 0. This slope corresponds to (dT/dt) in equation 9. Therefore, it is negligible. T= (Tf-Ti) – () (td-ti)- ()f (tf -td) …show more content…
Equation 11 is used to find the heat released in combustion of naphthalene or the energy of combustion (ΔE). qcomb= ΔUcomb*(mBA) + ΔUwire*(mwire) (11)
ΔUcomb and ΔUwire are the specific energies of benzoic acid and the iron fuse wire. They correspond to the values -26.41 kJ/g for benzoic acid and -6.68 kJ/g for iron.1 The change in temperature is assumed to be entirely from the result of the combustion of a substance and not from heat from the universe, i.e. this part of the apparatus is adiabatic (quniv=0). This is assumption is displayed in equation 12. qcal is the heat absorbed by the calorimeter. qcomb + qcal= quniv qconb = -qcal (12)
In order to use equation 13 it is also assumed that the temperature change of the water is the temperature change in the bomb calorimeter. The heat capacity of the bomb calorimeter (CVcal) was found to be 10.9kJ/K for the first trial of benzoic acid and 10.4kJ/K for the second trial. This gives a mean of