3) Introduction‎ > ‎

3.5) Enthalpy of Combustion of Gasoline and Diesel

 
    
The reaction of combustion of the gasoline is given by the following chemical equation:
 

and the equation of the reaction of combustion of the diesel is:
                                                                      

    
Thermodynamics
is the study of energy and it's transformations, and describes the energetic properties of gases, liquids, solids or mixtures, all this by understanding the relationship between work, heat, enthalpy, entropy, temperature, pressure, volume, and other parameters . The internal energy U is the parameter that is related to the sum of the potential and kinetic energy. At constant volume, the system passes from an initial state with internal energy Ui, to an final state Uf. The change in internal energy, ΔU, is the sum of the energy transferred as heat (q) for the system and the work done by the system (w):
 
ΔU = q + w
    
    
This equation
describes the First Law of Thermodynamics, the Energy Conservation. In bomb calorimetry, the system is closed at constant volume, there is no exchange of mass, although there is thermal variation and exchange of energy.
    In the literature found, the internal combustion energy of gasoline is 47,30 kJ/g and the internal combustion energy of diesel is 44,80 kJ/g.
 
 
    Calibration of the bomb calorimetry
 
    The calibration with benzoic acid aims to establish the relationship between the amount of heat liberated and the variation of temperature in the reaction. For this, it's necessary to determine the energy equivalent of the calorimeter, i.e. the amount of energy required to vary one unit the temperature.
    The theoretical equivalent energy for the combustion of acid benzoic is 790 J/K and the internal combustion energy for that compound (ΔcU0BA) is 42 kJ/g.
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