Gibbs energy change, of reaction, standard

The standard Gibbs energy change of reaction, is used ia the calculation of equilibrium compositions the standard heat of reaction, is used iu... 

Quantity K is the chemical reaction equilibrium constant for reactionyj and AG° is the corresponding standard Gibbs energy change of reaction (eq. 237). Although called a constant, fC is a function of T, but only of T. 

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]). 

Fig. 1.1 (a) The ionization enthalpies of dipositive lanthanide ions with configurations of the type [Xe]4f" (upper plot left-hand axis), (b) The standard Gibbs energy change of reaction 1 (lower plot right-hand axis estimated value ... 

Calculation of equilibrium conversions is based on the fundamental equations of chemical-reaction equilibrium, which in application require data for the standard Gibbs energy of reaction. The basic equations are developed in Secs. 15.1 through 15.4. These provide the relationship between the standard Gibbs energy change of reaction and the equilibrium constant. Evaluation of the equilibrium constant from thermodynamic data is considered in Sec. 15.5. Application of this information to the calculation of equilibrium conversions for single reactions is taken up in Sec. 15.7. In Sec. 15.8, the phase role is reconsidered finally, multireaction equilibrium is treated in Sec. I5.9.t... 

The final term AG° is the conventional way of representing the quantity GJ It is called the standard Gibbs energy change of reaction. 

The overall change in the Gibbs energy for the entire process, i.e., the sum of the changes for the five steps, is also the standard Gibbs energy change of reaction, because the overall result of the process is the conversion of reactants to products, all in their standard states. Therefore... 

Thus AG°/RT(= — InK) as given by Eq. (13.18) is readily calculated at any temperature from the standard heat of reaction and the standard Gibbs-energy change of reaction at a reference temperature [usually 298.15 K (25 C)], and from two functions which can be evaluated by standard computational procediues. 

---