Thermodynamic Data of the Reaction

Ammonia synthesis proceeds according to the following reaction (8)  

To fix a kilogram of nitrogen in ammonia requires reacting 2.4 m3 (STP) of hydrogen and 0.8 m3 (STP) of nitrogen. About 3.27 MJ of heat is evolved. Table 9 is a 

Chemical Equilibrium. The reaction equilibrium has been investigated experimentally and theoretically many times. Today, values for the equilibrium constant are available for pressures up to 350 MPa (3500 bar). 

Gillespie and Beattie [89] (see also [33]) were by for the most successful experimentally in establishing a firm basis for an analytical expression of the equilibrium constant in the range of industrial interest. The values in Tables 10 and 11 were calculated using their equation. A detailed description, with literature data and many tables, appears in [33]. A description of the equilibrium using the Redlich-Kwong equation of state is given in [90]. 

Heat of Reaction. Haber investigated the heat of reaction at atmospheric pressure [91]. Numerous authors have estimated the pressure dependence under various assumptions. Today, most people use the Gillespie-Beattie equation [92]. This equation was used in calculating the values in Table 12. For further data see, for example, [33]. Reference [93] contains test results for the range 120-200 MPa (1200 - 2000 bar) and 450-525 °C. Additional literature can be found in [94]. 

---

The reaction as defined by the lUBMB. The commentary gives information on the mechanism, the stereochemistry, or on thermodynamic data of the reaction. 

The results of these measurements can be compared with thermodynamic data of the reaction products. 

During charging and discharging of the cell, the terminal voltage U is measured between the poles. It should also be possible to calculate directly the thermodynamic terminal voltage from the thermodynamic data of the cell reaction. This value often differs slightly from the terminal voltage measured between the poles of the cell because of an inhibited equilibrium state or side reactions. 

Representative thermodynamic data for the reaction of monovalent and bivalent metal ions with the two isomers (A and B) of dicyclohexyl-18-crown-6 are given in Table 13. From these and similar reactions... 

Table 61 Thermodynamic Data for the Reaction of some Macro-cyclic Ligands with Silver(I) in Methanol at 25 °C...

Careful analyses of the thermodynamic data of the praseodymium and terbium oxides led to the construction of their RCL-O2 phase diagrams (Hyde et al., 1966 Hyde and Eyring, 1965). The cerium oxides were studied by means of X-ray powder diffraction (Bevan, 1955) and the CeOx-02 phase diagram was constructed from equilibrium reaction studies at oxygen pressures down to 10-24 atm and temperatures up to 1200 °C (Bevan and Kordis, 1964 Ricken et al., 1984). It is worth to notice that the phase diagrams of Ce0x-02, PrCb-Cb, and Tb0x-02 systems... 

Considering the thermodynamic parameters of the reaction, it has been determined that the silicic acid with a hexacoordinated atom of silicon H2[Si(OH)6] formed in die process of reaction displaces ammonium ion from phenolates, so that this acid is stronger than catechol. This is in agreement with our experimental data at the beginning of the reaction process the decrease in the pH of the reaction mixture from 7.16 to 5.85 was observed before the pH became constant. 

The large contribution of the inductive effect to the substituent constant a, and its relation to the entropic contribution (22) offer mechanistic insight into Hammett relationships. These facts show that in most cases the substituent mainly affects the molecular changes in solute-solvent interactions between the final and initial stages (thermodynamic data) of a reaction or between the transition and the ground states (kinetic data). 

Utilizing heat content, heat capacity and entropy data, together with the generalized fugacity diagram, make a thermodynamic study of the reaction... 

Because activation energies for most of the reactions of Table II were not available, T and P are fixed at standard conditions. The pH is also treated as a fixed variable to simulate our buffered sonication experiments. The computer code can be modified to correct the rate constants for different T or P (assuming that the necessary thermodynamic data for the reactions of Table II become available), or to treat pH as a variable species (by including H+ as a 23rd chemical species). 

The objective of the ECD and NIMS experiments is to measure the molar response of different compounds as a function of temperature. From these data the fundamental kinetic and thermodynamic properties of the reaction of thermal electrons with molecules and negative ions can be determined. The measurement is carried out in the same manner as the calibration of any detector. Known amounts of a compound are injected into the chromatograph and purified on a column, they then enter the detector. The response of the detector is normalized to the number of moles injected. When obtaining physical parameters, the detector temperature is changed and the procedure repeated. Since the molar response can vary by three to four orders of magnitude, the concentrations of the test molecule and the conditions in the detector at different temperatures must be taken into account. 

Acquisition of thermodynamic and kinetic data of the reactions of IS process (Bunsen reaction, HI concentration and decomposition with reactive distillation and SO3 catalytic decomposition). 

This chapter presents the chemical thermodynamic data set for selenium species which has been selected in this review. Table lll-l contains the reeommended thermodynamic data of the selenium species, Table III-2 the recommended thermodynamic data of chemical equilibrium reactions by which the selenium compounds and complexes are formed, and Table III-3 the temperature coefficients of the heat capacity data of Table lll-lwhere available (see Appendix E for additional selenium data, cf. Section 11.7). 

Table IV-1 contains the selected thermodynamic data of the auxiliary species and Table IV-2 the selected thermodynamic data of chemical reactions involving auxiliary species. The reason for listing both reaction data and entropies, enthalpies and Gibbs energies of formation is, as described in Chapter 111, that uncertainties in reaction data are often smaller than the derived, Af//° and AfG°, due to uncertainty accumulation during the calculations.

Spectroscopic data has been obtained that is consistent with the formation of four-membered ring adducts 61/62 as the kinetic products of the reaction. The step leading to these cyclic products has been shown to be reversible prolonged exposure of 61/62 to the reaction conditions led to the conversion of these metastable oxetanes to 63, the thermodynamic product of the reaction. The investigators have speculated that the formation of oxetane adducts in this study is a consequence of a slow silyl transfer step 60—>63. Thus, these observations highlight the fine balance that can exist between the various reaction pathways available to the adduct of the C-C bond-forming step (cf 60). 

The thermodynamic parameters of the reactions involved in Scheme (7-22) may be either calculated from thermochemical data or measured for a suitable model system. The first approach was used extensively by Enikolopyan s... 

The standard electrode potentials can be calculated from thermodynamic data of the substances participating in the equilibrium reaction. Electrode potentials contain additional contributions which depend on the composition of the mixed phases. These additional contributions are the origin for possible analytical applications. 

---