Gibbs energy reaction, standard molar

The first term on the right side of Eq. 11.8.2 is the standard molar reaction Gibbs energy, or standard molar Gibbs energy of reaction ... 

Some of the most useful experimentally-derived data for thermodynamic calculations are values of standard molar reaction enthalpies, standard molar reaction Gibbs energies, and standard molar reaction entropies. The values of these quantities for a given reaction are related, as we know (Eq. 11.8.21), by... 

The standard Gibbs free energy of reaction, AG°, is defined like the Gibbs free energy of reaction but in terms of the standard molar Gibbs energies of the reactants and products ... 

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... 

The compilation (Lias et al. 1988) is also the source of most of the data for the gas phase acidity, AGa in kJ mol 1 at 298 K. This is the standard molar Gibbs free energy of proton dissociation according to S(H) — S + H+ in the gas phase. Again, the equilibrium constant of a competition reaction,... 

The extent of the reaction of carbon dioxide with water to form carbonic acid is fairly well known—less than 1%. However, for thermodynamic purposes we make no distinction between the two nonionized species, C02 and H2C03. We are thus concerned with the sum of the concentration of these species, a quantity that can be determined experimentally. We must therefore develop the methods used to define the standard state of the combined nonionized species and the standard molar Gibbs energies of formation. 

Fig. 4-1. One-dimensional Gibbs energy diagram for an equilibrium reaction A B in the solvents 1 and 11. Ordinate standard molar Gibbs energies of the reactants A and B in solvents 1 and 11 Abscissa not defined. AG°(1) and AG°(11) standard molar Gibbs energies of reaction in solvents 1 and 11, respectively AGj°(A, 1 11) and AGj°(B, 1 11) standard molar Gibbs energies of transfer of the solutes A and B from solvent 1 to solvent 11, respectively [AGj°(A, 1 11) = G°(A in 1) - G°(A in 11), and AG°(B, 1 11) = G°(B in 1) - G°(B in 11)], cf. Eq. (2-12a) in Section 2.3 = transition state.

The standard molar Gibbs energy change for reaction (4-16), AG° = —RT In K, is then a measure of the relative acidity of HA and BH (or of the relative basicity of B and A ). Series of acids and bases have been studied to establish a scale of relative acidities in the same manner as p.K a values are determined in solution. 

Fig. 5-1. One-dimensional Gibbs energy diagram for reaction (5-1) in solution. Ordinate relative standard molar Gibbs energies of reactants, activated complex, and products Abscissa not defined, expresses only the sequence of reactants, activated complex, and products as they occur in the chemical reaction. AG° standard molar Gibbs energy of the reaction AG standard molar Gibbs energy of activation for the reaction from the left to the right.

Fig. 5-3. One-dimensional Gibbs energy diagram for a chemical reaction in two different solvents I and II [cf. Figs. 5-1 and 5-2). AGj and AG, standard molar Gibbs energies of activation in solvents I and II AG jj and AGj jj standard molar Gibbs energies of transfer of the reactants R and the activated complex from solvent I to solvent II, respectively.

Since the relationship between the equilibrium constant, K, for a reaction and the difference between the standard molar Gibbs energies of the products and reactants, AG°, is given by Eq. (7-2),... 

Eq. (7-1) essentially describes a relationship between standard molar Gibbs energies . It is often convenient to express linear Gibbs energy relationships in terms of ratios of constants by referring all members of a reaction series to a reference member of the series thus, the correlation in Eq. (7-1) can also be expressed by Eq. (7-4). 

In binary reciprocal univalent systems, the most dissociated is always the stable pair of salts. However, the correctness of the calculation was conditioned by the consistency and correctness of the molar conductivity values and especially by the correctness of the value of the standard Gibbs energy of the metathetical reaction. 

Partial molar Gibbs energy of component j standard Gibbs energy change for reaction i enthalpy... 

Here, AG° is the standard molar Gibbs energy change and K is the equilibrium constant for a reaction R is the gas constant (8.314 472 JIC moh ). The subscripts T and 6 denote the temperature to which a quantity pertains, the subscript p denotes constant pres-... 

Table VII-15 Standard molar Gibbs energies, enthalpies and entropies for the reactions + wHzOCl) Th COH) - + nit at 25°C.

A measurement of the equilibrium partial pressure of NH3 at a given temperature and pressure yields a value of AG° for this reaction, which is twice the conventional standard molar Gibbs energy of NH3 at this temperature. 

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