Standard thermodynamic properties

The standard state (and thus any standard thermodynamic property) of a pure solid refers to the pure substance in the solid phase under the pressure p of 1 bar (0.1 MPa). The standard state of a pure liquid refers to the pure substance in the liquid phase at p = 1 bar. When the substance is a pure gas, its standard state is that of an ideal gas at p = 1 bar (or, which is equivalent, that of a real gas at P = o). 

Chatteijee N. D. and Johannes W. (1974). Thermal stability and standard thermodynamic properties of synthetic 2M, muscovite KAl[AlSi30io(OU)2]. Contrib. Mineral Petrol, 48 89-114. 

In 1969 Wilhoit picked up where Burton had left off and compiled the standard thermodynamic properties AfG° and A H° of species involved in biochemical reactions. He recognized the problems involved in including species... 

The plot in Fig. 3.2 of the acid dissociation constant for acetic acid was calculated using equation 3.2-21 and the values of standard thermodynamic properties tabulated by Edsall and Wyman (1958). When equation 3.2-21 is not satisfactory, empirical functions representing ArC[ as a function of temperature can be used. Clark and Glew (1966) used Taylor series expansions of the enthalpy and the heat capacity to show the form that extensions of equation 3.2-21 should take up to terms in d3ArCp/dT3. 

The standard thermodynamic properties of ions are given in tables of standard thermodynamic properties at I = 0. The effect of ionic strength on ArG° for a chemical reaction is obtained by substituting equation 3.6-3 in equation 3.1-12 ... 

The calculations of standard thermodynamic properties discussed in the rest of this section are based on the assumption that the standard enthalpies of formation of species are independent of temperature in other words, the heat capacities of species are assumed to be zero. In the future when more is known about the molar heat capacities of species, more accurate calculations can be based on the assumption that the molar heat capacities are independent of temperature. When the heat capacities of species are equal to zero, the standard entropies of formation are also independent of temperature. Under these conditions the values of AfG at other temperatures in the neighborhood of 298.15 K can be calculated using... 

As we have seen in the preceding chapter, the standard thermodynamic properties of species in aqueous solutions are functions of ionic strength when they have electric charges. Substituting equation 3.6-3 for species j and for H + in equation 4.4-9 yields the standard transformed Gibbs energy of formation of species j as a function of pH and ionic strength at 298.15 K ... 

Equations 10.3-9 and 10.3-12 raise an issue about conventions for the hydrogen ion in thermodynamic tables. Since it is not possible to connect the standard thermodynamic properties of EI+ to those of molecular hydrogen, the convention is that AfG°(H + ) = 0 and Af//°(H + ) = 0 at each temperature. This indicates that the standard entropy of formation of a hydrogen ion AfS°(H+) should be taken as zero at each temperature, but, for historical reasons, the convention adopted in current thermodynamic tables is S°(H+) = 0 at each temperature. In principle, the value of S, (H + ) should be calculated from AfS EI4) for the formation reaction for H +. One way to write this reaction is... 

Since the standard thermodynamic properties of adenosine have been determined (ref. 7), new values are given for the ATP series. These changes do not change the values of apparent equilibrium constants that are calculated between reactants in this series, but will be useful in investigating the production of adenosine.. 

In a table of standard thermodynamic properties of compounds at 298 K, indicate whether each of the following is always zero, always positive, always negative, or none of the above (do this without looking at such a table and he able to explain your answer) ... 

A new thermodynamic model for the Cu(I,II)-HC1-H20 system was developed on the basis of the representative data on GuGl(s) solubility in aqueous solutions of HC1 in a concentration interval from 1 to 6 mol kg1 HG1 (Akinfiev, 2009). The model takes into account a number of aqueous Cu(I) species [Cu+, CuOH°, Cu(OH)2, CuC1°, CuClj, HCuCL ], aqueous Cu(II) species [Cu2 CuOH+, CuO°, HCuO , CuOJ- CuCl+, CuCL , GuGlg, CuClJ)] and a mixed Cu(I)/Cu(II) chloride aqueous complex, Cu2Cl . The thermodynamic approach used a modelling approach based on i) the standard thermodynamic properties of the listed above species ii) a model for the activity coefficients iii) use of HCh software (Shvarov, 1999). 

A long time ago chemists realized that the most efficient way to store thermodynamic data on chemical reactions is by making tables of standard thermodynamic properties of species. The NBS Tables of Chemical Thermodynamic Properties (4) gives AfG°, Af// and Sm° for species at 298.15 K at xero ionic strength. Since the standard molar entropy is not available for many species of biochemical interest, the standard entropies of formation Af S" are used. This property of a species is calculated by using... 

For example, the standard thermodynamic properties for p/fi and pK2 of atp at 298.15 K and three ionic strengths can be calculated as follows ... 

Note that the standard transformed Gibbs energy of formation of a species depends on the pH, but the standard transformed enthalpy of formation does not. When species have electric charges, their standard thermodynamic properties need to be adjusted for the ionic strength according to the extended Debye-Huckel theory (see Section 1.3) At zero ionic strength,... 

Now we need a program to calculate the function of pH and ionic strength that yields the change in a standard thermodynamic property for a biochemical reaction (3). 

Calculation of Standard Thermodynamic Properties of Species of a One-species Reactant from the Apparent Equilibrium Constant at 298.15 K and the Standard Transformed Enthalpy of Reaction at 313.15 K... 

Chapters 3-5 have described the calculation of various transformed thermodynamic properties of biochemical reactants and reactions from standard thermodynamic properties of species, but they have not discussed how these species properties were determined. Of course, some species properties came directly out of the National Bureau of Standard Tables (1) and CODATA Tables (2). One way to calculate standard thermodynamic properties of species not in the tables of chemical thermodynamic properties is to express the apparent equilibrium constant K in terms of the equilibrium constant K of a reference chemical reaction, that is a reference reaction written in terms of species, and binding polynomials of reactants, as described in Chapter 2. In order to do this the piiTs of the reactants in the pH range of interest must be known, and if metal ions are bound, the dissociation constants of the metal ion complexes must also be known. For the hydrolysis of adenosine triphosphate to adenosine diphosphate, the apparent equilibrium constant is given by... 

When the standard thermodynamic properties of species are unknown for two reactants in a biochemical equation, the Af Gy (7=0) and Af 7/y (/=0) of the more basic species of this reactant can be assigned values of zero, so Af Gi for that reactant can be calculated under the experimental conditions. These assigned values become conventions of the thermodynamic table, like Af G (H ) = 0 and Af 7/ (H+) = 0 at each temperature. As described in the preceding section, this was done for adenosine in dilute aqueous solution (3) in 1992, but the determination of the thermodynamic properties of adenosine in dilute aqueous (4) made it possible to drop this convention for the ATP series. 

Equation 14.2-7 is of special interest because of the connection it provides between experimental measurements and standard thermodynamic properties. The substitution of equations 14.2-5 and 14.2-6 into equation 14.2-7 yields... 

This is important for biochemistry because when it can be done, calculations can be made on the thermodynamics of the formation of a reactant all the way back to the elements it contains. Thanks to the research of Boeiro-Goates and coworkers, Af G° and Af//° are now known for adenosine (aq) (4), adenine (aq) (5), and inosine (aq) (6). This has made it possible to calculate the standard thermodynamic properties of species of AMP, ADP, ATP, IMP, IDP, and ITP as well. 

For thermodynamic analysis of the corrosion of iron alloys in supercritical water, the above computer program was modified based upon standard thermodynamic property extrapolation methods. 

Standard Thermodynamic Properties of Chemical Substances, CRC Press LLC, 2000. 

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