Showing papers on "Standard molar entropy published in 1982"

Theory of partial molar properties. Defining isochoric thermal capacity and isentropic compression at constant temperature and pressure, and introducing partial molar properties at constant temperature and molar volume, at constant molar entropy and pressure, and at constant molar entropy and molar volume

Abstract: The concept and properties of partial molar quantities are presented and discussed in a generalized fashion within a thermodynamic framework. X being any thermodynamic extensive property of a homogeneous phase of fixed composition, it is proposed to consider text-decoration:overlineXB(y, z) as a generalized partial molar property of substance B with respect to constant (y, z) whenever text-decoration:overlineXB(y, z)=(∂X/∂nB)y,z,n′ where n′ indicates that all n are held constant apart from nB, complies with the condition [graphic omitted]. This is shown to be true whenever the independent variables y and z, one thermal and the other mechanical, are intensive properties of the system.Concerning common partial molar properties, those defined at constant temperature and pressure, particular attention is paid to the partial molar isochoric thermal capacity text-decoration:overlineCV,B(T, p) and to the partial molar isentropic compression text-decoration:overlineKS,B(T, p). Contrary to generally accepted views, their relations with text-decoration:overlineCp,B(T, p) and with text-decoration:overlineKT,B(T, p), respectively, which are rederived directly from the equations relating the parent extensive properties, are far from being similar to the relations involving the corresponding molar properties. To express this behaviour, text-decoration:overlineCV,B(T, p) and text-decoration:overlineKS,B(T, p) are designated as non-Lewisian properties. A summary of thermodynamic relations among the usual text-decoration:overlineXB(T, p) properties (those of the Lewisian type) is presented, and it is suggested that non-partial molar quantities be defined in order to fill the place of non-Lewisian partial molar properties in the thermodynamic formalism for Lewisian ones.Generalized partial molar properties at constant temperature and molar volume text-decoration:overlineXB(T, Vm), at constant molar entropy and pressure text-decoration:overlineXB(Sm, p), and at constant molar entropy and molar volume text-decoration:overlineXB(Sm, Vm) are introduced and briefly discussed. Their general relations to text-decoration:overlineXB(T, p) are given and non-Lewisian properties are identified for each kind of partial molar properties. The origin of the non-Lewisian behaviour is ascribed to purely mathematical reasons. The concept of a ‘partial fractional property’ is introduced to allow intensive properties of the system which are not independent variables to be treated in a similar fashion to the extensive ones.Finally, some observations concerning the thermodynamic meaning of a partial molar property are made.

On the topological entropy of atomic liquids and the latent heat of fusion

Abstract: The authors identify the topological or configurational degrees of freedom in dense liquids as continuous line defects, labelled by the two-element group Z2. These defects are absent in perfect solids, and yield a topological contribution to the latent heat of melting. The topological entropy is universal (for dense atomic liquids) and equals R ln 2 per mole, as observed experimentally. The same value is obtained for the topological, molar entropy of melting of (loose) covalent liquids. The topological entropy of sublimation of atomic substances is also calculated to be 4.69 R per mole.

Thermodynamics and Electrochemistry of Simple Ions in Ammonia

Abstract: A compilation of the thermodynamics of simple ions in ammonia is given, based on thermodynamic data of their salts, on some electrochemical data and on those of solvated electrons. The final data are expressed in terms of the solvation enthalpies, solvation entropies and electrode potentials of the ions. With the uncertainties of the work function of the metals and that of the surface potential of the solvent, the concept that solvated electrons are partner of any redox equilibria allows the calculation of the “absolute” electrode equilibrium potential of any electrode in contact with the solution of any redox pair. This is exemplified for a cesium and a silver electrode in ammonia. - Finally the differences in the kinetics of solvated electrons in water and in ammonia with respect to the reaction with the solvent are expressed qualitatively by the transition state theory making use of the thermodynamic data of the solvated electrons. The high stability of electrons in ammonia is due to their very high positive partial molar entropy.

Monolayers of Alkylammonium Alkanesulfonates

Abstract: The surface pressure-area (π-A) curves for monolayers of cation-anion double long-chain salts, alkylammonium alkanesulfonates, were determined at the air-water interface by the Langmuir method. When the total chain length of cation and anion was constant, the transition pressure from the expanded to the condensed state in the monolayer was lowered as the chain length of cation elongated, and the lowest pressure at the transition point was observed in the case of the equal chain length of cation and anion. The lower the pressure at the transition point, the larger the value of the mean area per molecule at that point. The apparent molar entropy, enthalpy, and energy of transition from the expanded to the condensed phase were calculated from the temperature dependence of the transition pressure on the π-A curve. All the values calculated were negative. The magnitude in the changes of the apparent molar quantities was greatest when both a cationic and an anionic chain had the same length. These results were ...

An Empirical Estimation of Standard Entropy S_(293) for Some Complex Cations and the E-PH Diagrams of As-H_2O Systems at Elevated Temperature

Abstract: This paper deals with the Criss and Cobble's as well as Khodakovskii's methods on Calculating the free energy G°_T of yarious components in aqueous solutions The latter is recommended, but the calculating equation is simplified to turn into a simple form G°_T=G°_(298)+∝S°_(298)-β+ΥZ, here Z is the absolute value of charge, the ∝, β, and Y are constants dependent on temperatue and soluble species, and their values have been given。 An empirical estimation of the partial molal standard entropy S°_(298) for halogen complex cations MX_(m)~(n+) and oxy-cations MO_(m)~(n+), M(OH)_m~(n+) have been researched, here M represents metallic ions, m=1 or 2, and n is the charge。 The author presents an empirical equation S°_(298),absolute=3/2R In M+64-554 (zf/r_(12)) for the given complex cations as above, here f is the structure factor, an experimental value dependent on cation type, r_(12) is effective ionic radius (in Angstroms), M represents molecular weight, R is gaseous constant and Z is the charge。 Finally, the E-PH diagrams of As-H_2O systems at temperature 25°, 60°, 100° and 150℃ have been described