Reaction thermodynamics revisited

To determine how flux and free energy are related for systems not in equilibrium we consider, without loss of generality, the case where Nb/Na Keq and J 0. In a non-equilibrium steady state Na and Nb are held constant by pumping A molecules into the system, and pumping B molecules out of the system, at the steady state flux rate J. 

Next imagine that we are able to place a label on each molecule that converts from state B to state A. These particles we denote by A. Apart from the label, A molecules are identical in every way to unlabeled A molecules in this thought experiment. In addition, imagine that A molecules lose their label when they convert to B molecules. Thus if we continue to pump A and B molecules into and out of the system at the constant flux J, then a steady state will be reached for which Na, the number of labeled molecules in state A, is less than or equal to Na, the total number of labeled plus unlabeled molecules in state A. 

At the steady state conservation of mass requires that j+ NA, = j Nb. Because the ensemble of NAt molecules in state A is in equilibrium with the ensemble of Nb molecules in state B, 

Equation (3.9) holds for a reaction operating in any steady state, including thermodynamic equilibrium. In equilibrium, 7+ = J, and 

Thus it is trivial that Equation (3.9) holds in equilibrium. The more interesting case is a non-equilibrium steady state for which 

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All through the first and second edition, the work of main people who contributed to both the theory and applications of thermodynamics, transport processes, and chemical reactions has been visited and revisited. I acknowledge and greatly appreciate all these people. I am also thankful for the help I received from Dr. Yelizaveta P. Renfro and the production team of Macmillan India Ltd. for editing and reviewing the chapters. 

Now that we have a basic understanding of solvents and solutes, let s examine the thermodynamics of solubility in more detail. The concepts involved lead directly to the thermodynamics of reactions. The second section of this book delves into the kinetics and mechanisms of organic transformations, which are highly dependent upon the nature of the solvent and the reactants. Hence, many of the topics discussed above will be revisited in these discussions. However, because the thermodynamics of solutions affects reactions and molecular recognition (the topic of the next chapter), it makes sense to discuss the thermodynamics of reactions here also. Therefore, in this section we explore the thermodynamic driving force for solubility and chemical reactions. 

Chapter 5 begins with a look at the structure, nomenclature, and stability of alkenes—compounds that contain carbon-carbon double bonds—and then introduces some fundamental principles that govern the reactions of organic compounds. You will revisit how to draw curved arrows to show how electrons move during the course of a reaction as new covalent bonds are formed and existing covalent bonds are broken. Chapter 5 also discusses the principles of thermodynamics and kinetics, which are central to an understanding of how and why organic reactions take place. 

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