Advanced Topics in Equilibrium

Paul s Cathedral, London. [Pictor International/ Emissions over Europe estimated by Schopp and colleagues. [From R. F. Wright, T. Larssen, L Comarero, 

Picture Quest.] B. j. Crosby, R. C. Ferrier. R. HeHiwelt, M. Forsius, A. Jenkins, J. Kopacek, V. Mqjer, F. MofcJon, M. Posch, M. Rogora, and 

Schopp, Recovery of Acidified European Surface Waters, Environ. Sci. Technoi. 2005, 39,64A.] 

Limestone and marble are building materials whose main constituent is calcite, the common crystalline form of calcium carbonate. This mineral is not very soluble in neutral or basic solution (Kip = 4.5 X 10-9), but it dissolves in acid by virtue of two coupled equilibria, in which the reactions have a species in common—carbonate in this case  

Carbonate produced in the first reaction is protonated to form bicarbonate in the second reaction. Le Chatelicr s principle tells us that, if we remove a product of the first reaction, we will draw the reaction to the right, making calcite more soluble. This chapter deals with coupled equilibria in chemical systems. 

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Dissolution of Organic Compounds in Water from Organic Liquid Mixtures—Equilibrium Considerations (Advanced Topic)... 

Two chapters on activity coefficients and the systematic treatment of equilibrium from the sixth edition were condensed into Chapter 8. A new, advanced treatment of equilibrium appears in Chapter 13. This chapter, which requires spreadsheets, is going to be skipped in introductory courses but should be of value for advanced undergraduate or graduate work. New topics in the rest of this book include the acidity of metal ions in Chapter 6, a revised discussion of ion sizes and an example of experimental design in Chapter 8. pH of zero charge for colloids... 

One of the most attractive aspects of the science of chemistry is the way it all fits together. Typically, students first learn the basics of atomic and molecular structure add some knowledge of thermodynamics, kinetics, and equilibrium and then quickly start to apply these ideas to more advanced topics. For example, you may have already studied Chapters 2 through 6 of this book and seen how the ideas that you worked so hard to master in your previous chemistry experiences provide the basis for the study of coordination compounds. Or, perhaps you have read Chapters 7 and 8 on the structures and energetics of solid-state chemistry. Alternatively, you may have skipped directly from Chapter 1 to this point to start a study of the chemistry of the periodic table and the representative elements. In any case, no matter in what order you have started to make your way through the discipline we call chemistry, the ultimate goal is the development of an interconnected network of ideas that you can use to rationalize and predict a variety of chemical behavior. Nowhere is such a network more essential than in a study of what has become known as descriptive chemistry, the properties, structures, reactions, and applications of the elements and their most important compounds. 

The treatment of equilibrium solvation effects in condensed-phase kmetics on the basis of TST has a long history and the literature on this topic is extensive. As the basic ideas can be found m most physical chemistry textbooks and excellent reviews and monographs on more advanced aspects are available (see, for example, the recent review article by Tnihlar et al [6] and references therein), the following presentation will be brief and far from providing a complete picture. 

According to Birss and Truax (72), students are likely to experience confusion and difficulty with more advanced treatments of the subject. With regard to conceptual difficulties, the authors looked at the equilibrium potential, the reversal of sign of electrode reactions that are written as oxidations, and the differences between galvanic (electrochemical) and electrolytic cells. An approach for teaching these topics at the freshman level was then proposed. In this approach, concepts from thermodynamics and chemical kinetics are interwoven with those of electrochemical measurements. Very useful are... 

It is important to recognize that the small subset of matrix equations introduced in the main text (typically, restricted to real matrix elements) will be found sufficient to exploit the geometrical simplicity that underlies equilibrium thermodynamics. Nevertheless, it is useful to introduce the thermodynamic vector geometry in the broader framework of matrix theory and Dirac notation that is broadly applicable to the advanced thermodynamic topics of Chapters 11-13, as well as to many other areas of modem physical chemistry research. 

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