Thermodynamics Gibbs energy change , calculation

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... 

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... 

In several reports, Lamy et al. have developed in detail the different relationships that allow us to calculate several important thermodynamic parameters of DEFCs [13, 14]. The Gibbs energy change of ethanol (under standard conditions) is — 1,326.7 kJ/mol. Therefore, the electromotive force (EMF) of a DEFC is ... 

The practical importance of thermodynamic theory lies in the fact that, given certain basic data, its principles permit the exact calculation of other data and the state of equilibrium of systems under specified conditions. Thus thermodynamic theory will allow one to state the feasibility of a hypothetical reaction and the maximum yield of a desired product which is to be expected. Use of approximate expressions for this latter purpose may sometimes be justified. For example, the defining equation for standard Gibbs energy change at temperature Tis the expression ... 

We can calculate the thermodynamic value of K by using techniques discussed in Part 1 of this textbook. The standard-state Gibbs energy change of the reaction is 385.914 kJ mol- and the thermodynamic value of K is... 

Summing changes in Gibbs energy. A convenient feature of thermodynamic calculations is that if two or more chemical equations are summed, AG for the resulting overall equation is just the sum of the AG s for the individual equations as illustrated in Eqs. 6-17 to 6-20. The same applies for AH and AS. 

Once the species present in a solution have been chosen and the values of the various equilibrium constants have been determined to give the best fit to the experimental data, other thermodynamic quantities can be evaluated by use of the usual relations. Thus, the excess molar Gibbs energies can be calculated when the values of the excess chemical potentials have been determined. The molar change of enthalpy on mixing and excess molar entropy can be calculated by the appropriate differentiation of the excess Gibbs energy with respect to temperature. These functions depend upon the temperature dependence of the equilibrium constants. 

It should be noted that either the insertion or annihilation of the particle can be used to calculate the Gibbs energy of solvation, and both are related by a change of sign. With an appropriate method for solving the solubility calculations in aqueous solution, such as the one presented here, one can parameterize a model of C02 for a particular water model to reproduce these values over an extended thermodynamic window, such as over a desired temperature range that would encompass any type of brine aquifer. 

The direction of chemical reactions can always be predicted from thermodynamical data. Thus, if the Gibbs free energy change of a reaction is calculated,... 

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