Gibbs free energy yielding

Upon burial in the sediments, organic matter is microbially oxidized in a sequence dictated by the Gibbs Free Energy yield of each reaction (Froelich et at., 1979). The oxidants are used in this sequence respiration of oxygen,... 

The Gibbs free energy yield of carbon oxidation with S04 as a terminal electron acceptor is about 4-10 times lower than with oxygen. However, sulfide, the product of S04 reduction is an excellent electron donor the reaction of which with oxygen ... 

The fugacity function has been.introduced because its relation to the Gibbs energy makes it useful in phase equilibrium calculations. The present criterion for equilibrium between two phases is that G- = Gf for all species i, with the restriction that the temperature and pressure be constant and equal in both phases. Using Eqs. 9.2-10 and the equality of partial molar Gibbs free energies yields... 

We have seen in Chapter 11 that all partial molar properties must satisfy the Gibbs-Duhem equation, Eq. 11.6.3, which when applied to the molar excess Gibbs free energy yields (Problem 13.52) ... 

Within the framework of the same dielectric continuum model for the solvent, the Gibbs free energy of solvation of an ion of radius and charge may be estimated by calculating the electrostatic work done when hypothetically charging a sphere at constant radius from q = 0 q = This yields the Bom equation [13]... 

Since these mixing processes occur at constant pressure, // is the heat evolved or absorbed upon mixing. It is usually measured in a mixing calorimeter. The excess Gibbs free energy, is usually obtained from phase equilibria measurements that yield the activity of each component in the mixtureb and S is then obtained from equation (7.17). The excess volumes are usually obtained... 

The study of chemical equilibrium can detect thermodynamic constraints on the achievable conversion and selectivity. In this section we make use of the Gibbs free-energy minimization method available in Aspen Plus [9], We assume that both cyclohexanone and cyclohexanol are products. The curves in Figure 5.2 show the evolution of the phenol equilibrium conversion, yield and selectivity with the ratio hydrogen/phenol at temperatures of 180, 200, 220 °C and a pressure of 3 bar. 

The thermodynamic criterion for the equilibria CaCO, ) = Ca0(,) + C02 (,) is AG ° = -RT n Kp, where AG° is the change in Gibbs free energy of the reactants and products in their standard state, R is the gas constant, and Kp is the equilibrium constant. For this equilibria, A p = pco, for pressure in units of atmospheres. Values for AG are tabulated in the form AG° = a+ bT combining these expressions yields an exponential relationship between the partial pressure of CO2 and temperature for the above equilibria. Complete derivations and discussion of these equations may be found in physical chemistry textbooks such as references [13] and [14]. 

The determination of flow control coefficients is difficult, and requires the independent variation of the activity of all the enzymes within the pathway. Based on linear nonequilibrium thermodynamics, the kinetics of enzyme reactions can be described by the linear functions of the change in Gibbs free energy. This yields a direct relation between the elasticity coefficients and the change in Gibbs free energy for the reactions in a simple two-step pathway. 

Figure 2.5 Gibbs free energies for a system in which there are muitiple noninterconvertable crystalline phases, each with a different iattice energy (El = G, at T = 0 K) but all with the same entropy. All yield a liquid with the same free energy. Arrows show access to the different crystaiiine phases from the liquid. The crystal with the lowest melting point must be the one with the iowest lattice energy. It will be the one that melts to a liquid with the highest viscosity, and the one that therefore is the least likely to crystallize during cooling. When crystallization does not occur, the glassy state does.

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