Thermochemistry of Combustion

The specific heat ratio defined in Eq. (1.9) is 5/3 for monatomic molecules and 9/7 for diatomic molecules. Since the excitations of rotational and vibrational freedoms occur only over restricted temperatures, the specific heats determined by kinetic theory are different from the specific heats determined by experiments. However, the results obtained by the theory are valuable to understand the behavior of molecules and the process of energy conversion in the thermochemistry of combustion. Figure 1-1 shows the specific heats of real gases appearing in combustion. The specific heats of monatomic gases remain constant when temperature is increased as are determined by kinetic theory. The specific heats of diatomic and polyatomic gases are increased as the rotational and vibrational modes are excited by the increases of temperature. 

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