Gibbs free energy change of reaction

Having calculated the standai d values AyW and S" foi the participants in a chemical reaction, the obvious next step is to calculate the standard Gibbs free energy change of reaction A G and the equilibrium constant from... 

AG = Gibbs free energy change of reaction at the standard state, kcal/g mole... 

AG° is the standard Gibbs free energy change of reaction obtained from the standard energy of formation of pure components AG at 25 °C, P = 1 atm and a suitable aggregation state. Once having determined IQq in standard conditions, the van t Hoff equation may be used to calculate fQq at other temperatures, as follows ... 

STANDARD GIBBS FREE-ENERGY CHANGE OF REACTION 4.5... 

Figure 3. A complete ystematization of modem thermodynamics. Note (AG )t.p, (AG2)t.p and (AG)t.p are Gibbs free energy changes of reaction 1, reaction 2 and the whole system at constant temperature and pressure, respectively. X and J represent thermodynamic force and thermodynamic flux for irreversible process, respectively.

A chemical reaction will proceed to products in significant yield only if the standard Gibbs free energy change of reaction AG° is negative or at worst slightly positive, since the equilibrium constant K° for the reaction under standard conditions is... 

Gibbs free energy change of reaction [J/mol] Entropy change of reaction [J/mol K] Faraday constant [96,485 C/mol] oxygen flux density [mol/cm s] surface exchange coefficient [cm/s] partial oxygen pressure [bar] gas constant [8.314 J/mol K] ionic conductivity [S/cm] electronic conductivity [S/cm] temperature [K]... 

Gibbs free energy change of reaction (J moP ) enthalpy change of reaction (J moP ) thermodynamic flux (mol s ) equilibrium coefficient (depends) k column vector of kinetic coefficients (first order) (s )... 

From these data, the Gibbs free energy changes of Reaction 3.2 are calculated. Since... 

The term in parenthesis in the left-hand side of Equation 11.14 is the Gibbs free energy change of reaction 11.8. The next term is the electrical contribution to the electrochemical Gibbs free energy change of reaction 11.8 ... 

The standard Gibbs free-energy change of reaction, A G , is related to the enthalpy change of reaction and the entropy change of reaction (A S ). 

The method of calculating Gibbs free energy change of reaction uses an energy cycle similar to the enthalpy cycles you used to calculate the enthalpy change of reaction in Chapter 6 (see Figure 23.8). 

The Gibbs free energy change of reaction is also a measure of the feasibility of a reaction. Reactions with negative values of AGf are likely to be feasible (spontaneous), whereas those with positive values are less likely to be spontaneous. 

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