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3.3 Chemical Kinetics and Chemical Equilibrium 79
This approximation allows us to determine the concentration of A*
k f 1 A½ M½
A ½ ¼ ð3:43Þ
k b1 M½ k 2
*
Substituting [A ] into Eq. (3.39) leads to
dA½ k f 1 k 2 A½ M½
¼ ð3:44Þ
dt k b1 M½ k 2
k
Now, the rate of reaction constant k for the overall reaction A ! B þ C is
determined by
dA½
¼ k½A
dt
And it gives the overall reaction rate constant as,
k f 1 k 2 M½
k ¼ ð3:45Þ
k 2 k b1 M
½
3.4 Thermodynamics of Combustion System
Temperatures are assumed known in the preceding analyses. In case the tempera-
ture of the combustion product mixture is unknown yet, it has to be determined
from the combination of chemical equilibrium and thermodynamics. Related topics
are briefly reviewed as follows for the readers without related training background.
3.4.1 First Law of Thermodynamics
The first law of thermodynamics is about the conservation of energy; the total
energy of the thermodynamic system and its surrounding environment is conserved.
Physically, the first law states that, for a closed system, the change in the internal
energy is equal to the sum of the amount of heat energy supplied to the system and
the work done by the system on the surroundings. The first law of a combustion
system is mathematically described as
DU ¼ Q W ð3:46Þ
