Gibbs free energy change, for

The electromotive force of a cell can be related to the Gibbs free energy change for the cell reaction by combining equations (9.5), (9.90), and (3.96). We recall that... 

These equations are equivalent to a requirement that the Gibbs free energy change for each reaction (AG) be zero at equilibrium. 

Once the standard states for the various species have been established, one can proceed to calculate a number of standard energy changes for processes involving a change from reactants, all in their respective standard states, to products, all in their respective standard states. For example, the Gibbs free energy change for this process is... 

In order to have a consistent basis for comparing different reactions and to permit the tabulation of thermochemical data for various reaction systems, it is convenient to define enthalpy and Gibbs free energy changes for standard reaction conditions. These conditions involve the use of stoichiometric amounts of the various reactants (each in its standard state at some temperature T). The reaction proceeds by some unspecified path to end up with complete conversion of reactants to the various products (each in its standard state at the same temperature T). 

The enthalpy and Gibbs free energy changes for a standard reaction are denoted by the... 

The standard Gibbs free energy change for a reaction refers to the process wherein the reaction proceeds isothermally, starting with stoichiometric quantities of reactants each in its standard state of unit activity and ending with products each at unit activity. In general it is nonzero and given by... 

At 25 °C the standard Gibbs free energy change for the reaction... 

It can be shown (see Chapter 3) that the standard state Gibbs free energy change for this reaction is given by the difference between the standard state free energies of the products minus the reactants and can be related to the partial pressure of the gaseous species ... 

The variation of the standard state Gibbs free energy change for the oxidation reaction at any temperature from experimentally measured variations in Po2,e r can be fitted to an equation of the form ... 

The Gibbs free energy change for total combustion of such molecules always has a larger negative value than partial oxidation. Hence a catalyst to control kinetically the oxidation process is an absolute necessity. By choosing the right conditions and the proper type of catalyst, the oxidation process can be directed towards intermediates which do not react further. 

An important motivation for studying entropy changes at low temperature is to obtain reaction entropies AS (5.76) that could be combined with thermochemically measured reaction enthalpies A7/rxn to give the Gibbs free energy changes for chemical reactions. Starting from the observation that... 

Figure 12.1 Gibbs free energy changes for the scheme...

Figure 12.4 Gibbs free energy changes for the schemes in Figures 12.1 and 12.2, When the enzyme is complementary in structure to (1) the substrate (dashed curve), and (2) the transition state (isolid curve). (AG is algebraically negative, and AGj and AGr are positive.)...

Method of Amidon and Anik The method of Amidon and Anik [9] applicable to hydrocarbons and is based on the group additivity of the surface area. The approach is to model the Gibbs free energy change for the vaporization process, AGV, as an additive parameter according to the following equation ... 

We represent A///° and A/G° as the standard enthalpy and Gibbs free energy changes for the reaction in which the chemical substance is formed from the elements in their stable form, as they occur in nature at T = 298.15 K.rr For ions in solution, the values tabulated are relative to the standard enthalpy and Gibbs free energy of formation of the H+ ion being set equal to zero.ss... 

The value of the Gibbs free energy change for a chemical reaction at the temperature specified is given by the difference in Gibbs free energy between the products and the reactants. 

Consider the following process Starting with a small amount of a system with concentrations Cj at T and P, we add components to the system, at constant T and P, in the proper ratio to keep the concentrations constant. We can integrate Eq. (7) for the Gibbs free-energy change for this process ... 

The results of the DFT calculations for various stable C2H.V species and transitions states on Pt(lll) and Pt(211) are summarized in Table V, which also shows entropy changes for the various steps, as estimated from DFT calculations of the vibrational frequencies of the various adsorbed C2H species and transition states on 10-atom platinum clusters (55). Table V also includes estimates of the standard Gibbs free energy changes for the formation of stable C2H surface species and activated complexes responsible for C-C bond cleavage at 623 K. These estimates were made by combining... 

Gibbs free energy change,, for methane transformation reactions (10)... 

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