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4. Entropy in Chemical Processes


Balance of entropy in chemical systems

The balance of entropy for chemical systems is precisely the same as for any other system (see Chapter 3). The entropy of a system changes due to exchange and production. Exchange can be the result of conduction, convection, and radiation.
Law of balance. The rate of change of entropy of a system is determined by the sum of all process quantities (flows, sources, production rates):
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Figure 1

Entropy production in chemical conversions

Like any other process, chemical conversions are usually irreversible (typical exemption: phase transfromations). Very often, they are (almost) completely irreversible, such as diffusion or slow burning of a fuel. In these latter processes, the energy released in the chemical transformation is used only for the production of entropy (see Fig. 2):
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Figure 2