ELEMENTARY STATISTICAL THERMODYNAMICS

N. O. Smith, Elementary Statistical Thermodynamics—-A Problems Approach, Plenum Press, New York, 1982. 

From elementary statistical thermodynamics we know that the Gibbs free energy of the system is... 

Smith, N. O. (1982). Elementary Statistical Thermodynamics. Plenum, New York. 

From elementary statistical thermodynamics we know that the equilibrium constant can be written in terms of the partition functions of the individual molecules taking part in a reaction. These quantities represent the sum over all energy states in the system—translational, rotational, vibrational, and electronic. The probability that a molecule will be in a particular energy state, f ,-, is given by the Boltzmann law,... 

Elementary statistical thermodynamics or even phenomenological thermod5mamics entropy, free energy... 

For example, the measured pressure exerted by an enclosed gas can be thought of as a time-averaged manifestation of the individual molecules random motions. When one considers an individual molecule, however, statistical thermodynamics would propose its random motion or pressure could be quite different from that measured by even the most sensitive gauge which acts to average a distribution of individual molecule pressures. The particulate nature of matter is fundamental to statistical thermodynamics as opposed to classical thermodynamics, which assumes matter is continuous. Further, these elementary particles and their complex substmctures exhibit wave properties even though intra- and interparticle energy transfers are quantized, ie, not continuous. Statistical thermodynamics holds that the impression of continuity of properties, and even the soHdity of matter is an effect of scale. 

The most common states of a pure substance are solid, liquid, or gas (vapor), state property See state function. state symbol A symbol (abbreviation) denoting the state of a species. Examples s (solid) I (liquid) g (gas) aq (aqueous solution), statistical entropy The entropy calculated from statistical thermodynamics S = k In W. statistical thermodynamics The interpretation of the laws of thermodynamics in terms of the behavior of large numbers of atoms and molecules, steady-state approximation The assumption that the net rate of formation of reaction intermediates is 0. Stefan-Boltzmann law The total intensity of radiation emitted by a heated black body is proportional to the fourth power of the absolute temperature, stereoisomers Isomers in which atoms have the same partners arranged differently in space, stereoregular polymer A polymer in which each unit or pair of repeating units has the same relative orientation, steric factor (P) An empirical factor that takes into account the steric requirement of a reaction, steric requirement A constraint on an elementary reaction in which the successful collision of two molecules depends on their relative orientation. 

By applying the machinery of statistical thermodynamics we have derived expressions for the adsorption, reaction, and desorption of molecules on and from a surface. The rate constants can in each case be described as a ratio between partition functions of the transition state and the reactants. Below, we summarize the most important results for elementary surface reactions. In principle, all the important constants involved (prefactors and activation energies) can be calculated from the partitions functions. These are, however, not easily obtainable and, where possible, experimentally determined values are used. 

Table 10.4 lists the rate parameters for the elementary steps of the CO + NO reaction in the limit of zero coverage. Parameters such as those listed in Tab. 10.4 form the highly desirable input for modeling overall reaction mechanisms. In addition, elementary rate parameters can be compared to calculations on the basis of the theories outlined in Chapters 3 and 6. In this way the kinetic parameters of elementary reaction steps provide, through spectroscopy and computational chemistry, a link between the intramolecular properties of adsorbed reactants and their reactivity Statistical thermodynamics furnishes the theoretical framework to describe how equilibrium constants and reaction rate constants depend on the partition functions of vibration and rotation. Thus, spectroscopy studies of adsorbed reactants and intermediates provide the input for computing equilibrium constants, while calculations on the transition states of reaction pathways, starting from structurally, electronically and vibrationally well-characterized ground states, enable the prediction of kinetic parameters. 

This volume is addressed mainly to anyone interested in the life sciences. There are, however, a few minimal prerequisites, such as elementary calculus and thermodynamics. A basic knowledge of statistical thermodynamics would be useful, but for understanding most of this book (except Chapter 9 and some appendices), there is no need for any knowledge of statistical mechanics. 

Elementary and advanced treatments of such cellular functions are available in specialized monographs and textbooks (Bergethon and Simons 1990 Levitan and Kaczmarek 1991 Nossal and Lecar 1991). One of our objectives in this chapter is to develop the concepts necessary for understanding the Donnan equilibrium and osmotic pressure effects. We define osmotic pressures of charged and uncharged solutes, develop the classical and statistical thermodynamic principles needed to quantify them, discuss some quantitative details of the Donnan equilibrium, and outline some applications. 

Let us consider the compounds which show a small deviation from the stoichiometric composition and whose non-stoichiometry is derived from metal vacancies. The free energy of these compounds, which take the composition MX in the ideal or non-defect state, can be calculated by the method proposed by Libowitz. To readers who are well acquainted with the Fowler-Guggenheim style of statistical thermodynamics, the method here adopted may not be quite satisfactory however, the Libowitz method is understandable even to beginners who know only elementary thermodynamics and statistical mechanics. It goes without saying that the result calculated by the Libowitz method is essentially coincident with that calculated by the Fowler-Guggenheim method. 

Thermodynamics is based on the atomistic view, that is, that matter consists of elementary particles such as atoms and molecules that cannot be divided into smaller units. The three different states of matter are the result of the simultaneous interaction of a very large number, usually N = Na =6.02x 1023, of elementary particles. Thus, the macroscopic behavior of an ensemble of particles can be mathematically described as a state function that can be related to the individual behavior on a molecular scale, leading to the scientiLcally rigorous framework of statistical thermodynamics (Gcpel and Wiemhcfer, 2000). 

Chapter 5 gives a microscopic-world explanation of the second law, and uses Boltzmann s definition of entropy to derive some elementary statistical mechanics relationships. These are used to develop the kinetic theory of gases and derive formulas for thermodynamic functions based on microscopic partition functions. These formulas are apphed to ideal gases, simple polymer mechanics, and the classical approximation to rotations and vibrations of molecules. 

As previously, the sources on statistical thermodynamics are hardly numerable. Conciseness in them struggles with comprehensibility and both lose. Elementary information is given in physical chemistry courses already mentioned [1,2]. More fundamental courses are [3] - a rather physical one and [4] - a classical text on this subject. An interesting approach based on consistent usage of a single quantity - the entropy - is described in [5]. 

Planck s constant was discovered as part of the solution to a nineteenth century conundrum in physics, known as the black-body problem. The challenge was to model the wavelength distribution of radiation emitted through the aperture in a closed cavity at various temperatures6. The standard equations of statistical thermodynamics failed to produce the observed spectrum, unless it was assumed that the energy of radiation with frequency v was an integral multiple of an elementary energy quantum hv. 

Much more can be said about the magnitude of pre-exponcntial factors and activation energies of elementary processes based on statistical thermodynamics applied to collision and reaction-rate theory [2, 61], but in view of the remark above one should be cautious in their application and limit it to well-defined model reactions and catalyst surfaces. 

Most readers of this text have been exposed to probability theory concepts (Section 1.1.1) in an elementary course in statistical thermodynamics. As outlined in Section 1.2.2, a state of a classical. V-particle system is fully characterized by the 6/V-dimensional vector = (n,r2,...,rv, Pi, P2> Pv) (a point in the... 

Elementary statistical thermotfynamics or even phenomenological thermodynamics entropy, free energy (necessary). 

The objective and mode of thinking of statistical thermodynamics, its elementary tools, and model building are directly relevant to polymer physics. This article introduces the subject and relevant key references from a modern point of view. Perhaps the best introductory material is the problem source book (1,2), while Reference 3 is a standard reference. Minimum prerequisites are the rudiments of thermodynamics (4,5), and mechanics (6,7). Understanding of probability is very helpful (8). 

A good elementary discussion of statistical thermodynamics is given by T. L. Hill, Introduction to Statistical Thermodynamics (Reading, Mass. Addison-Wesley, 1960). See especially Chapter 3. 

Effects of the non-ideality of adsorbate are incorporated here through the introduction of a dependence of potential V, diffusion coefficient and rate constants of chemical reactions in the operator X. on the distribution function gc- These dependencies can be found from dynamical models of elementary processes, statistical thermodynamics of equilibrium and nonequilibrium processes, and from experimental data (see, e.g., (Croxton 1974)). 

The equations of isothermal kinetics (8.3.7)-(8.3.9) for the one-particle distribution function CcUi include lateral interactions both via the dependence of the transition probabilities on the coverage (the mean-field approximation) and via direct correlations between elementary processes in different cells. The strict consideration of the problem of lateral interaction may be given by methods of statistical thermodynamics. 

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