Gibbs energy reaction, calculation with

The authors also evaluated the enthalpy of the dimerisation reaction 2SnSe(g) Sn2Sc2(g) to be A,// (298.15 K) = -(194.6 + 22.0) kJ-mol in a third law analysis of measurements made in the temperature range 936 to 991 K.. No evaluation was made according to the second law because of the short temperature range. The third law evaluation employed Gibbs energy functions calculated from parameters estimated by comparison with the isoelectronic molecules As4(g) and Sb4(g). In the absence of better values of the molecular parameters, no recalculation was made by the review. 

Table 3 Thermodynamics for the major simple reductive reactions of EC/VC in electrolyte solutions (molar Gibbs free energies are calculated with the cluster (EC)Lr(VC)-B3PW91/6 31 l++G(d,p)//B3PW91/6-31G(d)).

Table 3.1 Gibbs energy barriers calculated by Ariafaid and Yates for the transmetalation reaction with different ligands L [54]...

The standard Gibbs-energy change of reaction AG° is used in the calculation of equilibrium compositions. The standard heat of reaclion AH° is used in the calculation of the heat effects of chemical reaction, and the standard heat-capacity change of reaction is used for extrapolating AH° and AG° with T. Numerical values for AH° and AG° are computed from tabulated formation data, and AC° is determined from empirical expressions for the T dependence of the C° (see, e.g., Eq. [4-142]). 

Complex Clieinical-Reaction Equilibria When the composition of an equilibrium mixture is determined by a number of simultaneous reactions, calculations based on equilibrium constants become complex and tedious. A more direct procedure (and one suitable for general computer solution) is based on minimization of the total Gibbs energy G in accord with Eq. (4-271). The treatment here is... 

When the kinetics are unknown, still-useful information can be obtained by finding equilibrium compositions at fixed temperature or adiabatically, or at some specified approach to the adiabatic temperature, say within 25°C (45°F) of it. Such calculations require only an input of the components of the feed and produc ts and their thermodynamic properties, not their stoichiometric relations, and are based on Gibbs energy minimization. Computer programs appear, for instance, in Smith and Missen Chemical Reaction Equilibrium Analysis Theory and Algorithms, Wiley, 1982), but the problem often is laborious enough to warrant use of one of the several available commercial services and their data banks. Several simpler cases with specified stoichiometries are solved by Walas Phase Equilibiia in Chemical Engineering, Butterworths, 1985). 

One main advantage of such a power source is the direct transformation of the chemical energy of methanol combustion into electrical energy. Hence, the reversible cell potential, can be calculated from the Gibbs energy change, AG, associated with the overall combustion reaction of methanol (1), by the equation ... 

The Van t Hoff isotherm establishes the relationship between the standard free energy change and the equilibrium constant. It is of interest to know how the equilibrium constant of a reaction varies with temperature. The Varft Hoff isochore allows one to calculate the effect of temperature on the equilibrium constant. It can be readily obtained by combining the Gibbs-Helmholtz equation with the Varft Hoffisotherm. The relationship that is obtained is... 

Practically in every general chemistry textbook, one can find a table presenting the Standard (Reduction) Potentials in aqueous solution at 25 °C, sometimes in two parts, indicating the reaction condition acidic solution and basic solution. In most cases, there is another table titled Standard Chemical Thermodynamic Properties (or Selected Thermodynamic Values). The former table is referred to in a chapter devoted to Electrochemistry (or Oxidation - Reduction Reactions), while a reference to the latter one can be found in a chapter dealing with Chemical Thermodynamics (or Chemical Equilibria). It is seldom indicated that the two types of tables contain redundant information since the standard potential values of a cell reaction ( n) can be calculated from the standard molar free (Gibbs) energy change (AG" for the same reaction with a simple relationship... 

K is the thermodynamic equilibrium constant which is only dependent on T, and ArG° is the standard reaction Gibbs energy of the reaction, which can be calculated with... 

Dipole moments of solutes are also involved in the so-called reaction-field theory1112 which predicts generally the Gibbs energy of solvation, and from it the stability of con-formers as dependent on solvents. Besides the dipole the quadrupole moment is also taken into the calculations. For instance, conformational equilibria of cyclic halo ketones were predicted from the dipole moments of the two conformers with fair success13. However, the whole theory was criticised1415 that there is too much arbitrariness in the... 

The calculation of the equilibrium composition of a system of chemical reactions with equcalcc is based on minimizing the Gibbs energy subject to the conservation condition An = nc. This is accomplished by using a Lagrangian L defined by... 

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