Gibbs enthalpy

The effect of pressure on chemical equilibria and rates of reactions can be described by the well-known equations resulting from the pressure dependence of the Gibbs enthalpy of reaction and activation, respectively, shown in Scheme 1. The volume of reaction (AV) corresponds to the difference between the partial molar volumes of reactants and products. Within the scope of transition state theory the volume of activation can be, accordingly, considered to be a measure of the partial molar volume of the transition state (TS) with respect to the partial molar volumes of the reactants. Volumes of reaction can be determined in three ways (a) from the pressure dependence of the equilibrium constant (from the plot of In K vs p) (b) from the measurement of partial molar volumes of all reactants and products derived from the densities, d, of the solution of each individual component measured at various concentrations, c, and extrapolation of the apparent molar volume 4>... 

Table 5. Reaction energies for the hydration of platinum complexes subscript denotes a reaction, and a denotes activation energies or Gibbs enthalpies. Index means activation energies corrected on the proper reactant conformer.

Fig. 3.1. Temperature profiles of the association constant K soc (dash-dotted line), the enthalpy AH (dashed line), the entropy as TAS (dotted line) and the resultant Gibbs enthalpy C (solid line) for a host-guest complexation characterized by (panel A)...

In artificial host-guest systems, the range in Gibbs enthalpy is rather limited (Kassoc varies between 10 and 10 M corresponding to AG" of —6 to —40... 

Analogous studies on the dimerization of cyclopentadiene in water revealed a stabilization of the transition structure relative to the initial structure as a result of a difference in solvation of 1.7 kcalmol. Unfortunately, at least to our knowledge, reliable experimental data for this process are not available. Recently, in a similar approach, the Gibbs enthalpies of hydration of the Diels-Alder reaction of cyclopentadiene with isoprene and methyl vinyl ketone were determined. Surprisingly, it was observed that water stabilized the transition structure of the cyclopentadiene - - isoprene reaction more than that of the... 

The effect of pressure on chemical equilibria and rates of reaction can be described by the well-known relationship between pressure and Gibbs enthalpy of reaction and activation, respectively (Scheme 2.1). The volume of reaction and... 

Tab. 2.10. Volume of reaction, AV, van der Waals volumes of reaction AVw, enthalpies, entropies, and Gibbs enthalpy of reaction calculated for the hypothetical cyclizations of 1-alkenes to cycloalkanes by means of the corresponding thermodynamic parameters [76].

A graphical method for calculating the equilibrium values consists of the direct calculation of the Legendre transformation of the molar-free Gibbs enthalpy, which is essentially the chemical potential. 

In Fig. 8.2, leftdown the ordinary plot of the reduced pressure p against the reduced volume p is shown. Left up of the integral shows the molar reduced Helmholtz energy or some kind of chemical potential. The Legendre transformation of this function is the molar reduced Gibbs enthalpy, or the reduced chemical potential as function of temperature and pressure. Recalling that... 

Fig. 18.8 Free Gibbs enthalpy of the species involved in the reaction mechanisms. The plot is reduced by the free Gibbs enthalpy of the reactant. Therefore, the plot starts at zero...

The Gibbs enthalpy is equal to the reversible work of the reaction. The reversible efficiency is equal to the ratio of the Gibbs enthalpy to the reaction enthalpy... 

Duf] Thermal analysis Gibbs enthalpies of formation of CaFesOs, CaFe204, CaFc507... 

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