In some cases, a literature source of thermodynamic data may exist, allowing one to perform the conversion. Fortunately, standard references (such as Refs. 168 and 180) frequently tabulate both the condensed and gas phase thermochemistry values. When that is not the case, the following relations may be used, where the enthalpies and entropies of vaporization and fusion must be at 25 °C [Pg.200]

It often happens that we do not know the standard entropies of vapour and condensed phase, and in such cases we may, for approximate calculations, employ an empirical rule to estimate the value of A s at atmospheric pressure. The most important of these is Tronton s rule, which states that the entropy of vaporization at the normal boihng point i.e. when liquid and vapour co-exist at 1 atm. pressure) has a value of about 20 cal./deg. mole. Thus [Pg.198]

Use the Third Law to calculate the standard entropy, S°nV of quinoline (g) p — 0.101325 MPa) at T= 298,15 K. (You may assume that the effects of pressure on all of the condensed phases are negligible, and that the vapor may be treated as an ideal gas at a pressure of 0.0112 kPa, the vapor pressure of quinoline at 298.15 K.) (c) Statistical mechanical calculations have been performed on this molecule and yield a value for 5 of quinoline gas at 298.15 K of 344 J K l mol 1. Assuming an uncertainty of about 1 j K 1-mol 1 for both your calculation in part (b) and the statistical calculation, discuss the agreement of the calorimetric value with the statistical [Pg.198]

For areal gas or for a condensed phase, (9 V/9T)p is the thermal expansion coefficient of the material at constant pressure, a measurable quantity, so entropy variations with pressure can be easily calculated. (dV/9T)p is very small for condensed phases, and entropy is hardly sensitive to pressure variations in liquids and solids. In any case, the standard entropy is defined as the entropy at unit pressure (usually 1 atm, but sometimes also 1 bar). For a reversible process in which only F-V work is exchanged. [Pg.182]

Here, k(is the rate constant vk the stoichiometric coefficients of the kth component in the ith reaction of reagents and products, correspondingly A, the equilibrium constants the number of sites occupied by surface substance j of condensed phase n F," the surface site density in the th phase standard state and hk and sk the enthalpy and the entropy of the Arth substance. [Pg.490]

The reaction and activation free energies (AG, AG at 298 K and 1 atm) were evaluated for standard conditions using computed harmonic frequencies. In the study of monomer association and displacement events of the co-oUgomer-ization reaction, a process that occurs in the Uquid phase [5b], the solvation entropy for monomer complexation was approximated as being half of its gas-phase value. This is considered as a rehable estimate of the entropy contribution in condensed phase [13aj. [Pg.194]

Another valuable source is the thermochemical property database assembled by Burcat and Ruscic [29], which is available online at ftp // ftp.technion.ac.il/pub/supported/aetdd/thermodynamics/. This collection is regularly updated by Prof. Burcat. It contains data for 1500 species, presented in the form of polynomial coefficients that can be used to compute the enthalpy, entropy, and heat capacity as a function of temperature. While Burcat s tables include a number of aluminum-oxygen compounds, they do not happen to include the aluminum-chlorine species that we have been using as an example. Of course, there are many other handbooks and compilations of thermodynamic properties. However, the vast majority of these focus on organic compounds and/or condensed phase species. Standard handbooks, such as the CRC Handbook of Chemistry and Physics, rarely have any information not included in the sources cited above. [Pg.201]

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