Solid state thermodynamic data

In Guo, after the very fast protonation of the electron adduct by water at the heteroatom [k > 107 s 1, von Sonntag 1991 Candeias et al. 1992 at 0(6), N(3) or N(7), cf. reaction (180)], a rapid transformation occurs [reaction (181) k in H20) = 1.2 x 106 s k(in D20) = 1.5 x 10s s 1] which is also catalyzed by phosphate buffer (k = 5.9 x 107 dm3 mol-1 s 1) which has been attributed to a protonation at C(8) (Candeias et al. 1992). This assignment is based upon solid-state EPR data, where C(8)-H--adduct is the thermodynamically most stable H -adducl radical (Rakvin et al. 1987 for DFT calculations see Naumov and von Sonntag, unpubl. results). The high solvent kinetic isotope effect of ku/ko = 8 is a strong indication that a proton is transferred in the rate-determining step. The magnitude of the rate of phosphate buffer catalysis points to a protonation at carbon (for a similar reaction observed with the Thy radical anion see Table 10.20). The C(8)-H -ad-duct has a pKa value of 5.4 [equilibrium (182)]. 

Determination of the basic thermodynamic properties of the rare earth trifluorides remains incomplete. This is in part due to experimental difficulties, and only one direct calorimetric measurement has been reported. The enthalpy of formation, AH 29s, of YF3 (-410.7 0.8 kcal/mole) has been measured by fluorine bomb calorimetry (Rudzitis et al., 1965). In an expansion of earlier work, Polyachenok (1967) has obtained values for several trifluorides (La, Pr, Nd, Gd, Er) by an equilibrium exchange reaction RCbi -f-A1F3( ->RF3(0 +AICl3(g). Solid state emf data have been reported by Skelton and Patterson (1973) for the trifluorides of Nd, Gd, Dy and Er. Similar measurements have been described by Rezukhina et al. (1974) for the trifluorides of La, Pr and Y. The AHt-m values are 5-10 kcal/mole more negative than values reported earlier. 

Thermodynamic data show that the stabilities of the caesium chloride-metal chloride complexes are greater than the conesponding sodium and potassium compounds, and tire fluorides form complexes more readily tlrair the chlorides, in the solid state. It would seem that tire stabilities of these compounds would transfer into tire liquid state. In fact, it has been possible to account for the heats of formation of molten salt mixtures by the assumption that molten complex salts contain complex as well as simple anions, so tlrat tire heat of formation of the liquid mixtures is tire mole fraction weighted product of the pure components and the complex. For example, in the CsCl-ZrCU system the heat of formation is given on each side of tire complex compound composition, the mole fraction of the compound... 

Another oxyfluoride, PuOF4(c), has recently been reported (35) as a product of controlled hydrolysis of PuFg dissolved in anhydrous HF and precipitation from the solution. Again, no thermodynamic data are available but it appears that the compound is of very limited stability although stable in the solid state at room temperature, it is reported to decompose in the presence of liquid HF according to reaction (8)... 

Studies of the thermodynamics of formation of complexes of zinc with 2,2 -bipyridine in the presence of halide and thiocyanate ions in DMF has been carried out.205 The zinc complexes of 2,2 -bipyridine with A-(benzenesulfonyl)glycine and A-(toluene- -sulfonyl)glycine were synthesized and infrared data implied a structural analogy with the cadmium complexes. This suggests that the zinc promotes sulfonamide nitrogen deprotonation in the amino acid ligands in the solid state.206... 

Note These data have been obtained from the complete thermodynamic data tabulated in Kubaschewski et al. (loc. cit.), with the approximation of the simple two-term equation. This should serve for calculations not requiring an accuracy of better than 2kJmol 1 02, which is normally the case for industrial applications. Solid state crystal transformations which usually only have relatively small heats of transformation, have been ignored. 

Figure 8.15 Calculated composition versus oxygen stoichiometry curves for Lai- SrjCoCb-s. [The two experimental points are taken from data in A. N. Petrov, V. A. Cherepanov, and A. Y. Zuev, Thermodynamics, Defect Structure and Charge Transfer in Doped Lanthanum Cobaltites An Overview, J. Solid State Electrochem., 10, 517-537 (2006).]...

Reaction kinetics. The time-development of sorption processes often has been studied in connection with models of adsorption despite the well-known injunction that kinetics data, like thermodynamic data, cannot be used to infer molecular mechanisms (19). Experience with both cationic and anionic adsorptives has shown that sorption reactions typically are rapid initially, operating on time scales of minutes or hours, then diminish in rate gradually, on time scales of days or weeks (16,20-25). This decline in rate usually is not interpreted to be homogeneous The rapid stage of sorption kinetics is described by one rate law (e.g., the Elovich equation), whereas the slow stage is described by another (e.g., an expression of first order in the adsorptive concentration). There is, however, no profound significance to be attached to this observation, since a consensus does not exist as to which rate laws should be used to model either fast or slow sorption processes (16,21,22,24). If a sorption process is initiated from a state of supersaturation with respect to one or more possible solid phases involving an adsorptive, or if the... 

This solid solution still makes up the bulk of the solid particles after equilibration in an aqueous solution (59), since solid state diffusion is negligible at room temperature in these apatites (60), which have a melting point around 1500°C. These considerations and controversial results justify a thermodynamic analysis of the solubility data obtained by Moreno et al (58 ). We shall consider below whether the data of Moreno et al (58) is consistent with the required thermodynamic relationships for 1) an ideal solid solution, 2) a regular solid solution, 3) a subregular solid solution and 4) a mixed regular, subregular model for solid solutions. 

Data for a large number of organic compounds can be found in E. S. Domalski, W. H. Evans, and E. D. Hearing, Heat capacities and entropies in the condensed phase, J. Phys. Chem. Ref. Data, Supplement No. 1, 13 (1984). It is impossible to predict values of heat capacities for solids by purely thermodynamic reasoning. However, the problem of the solid state has received much consideration in statistical thermodynamics, and several important expressions for the heat capacity have been derived. For our purposes, it will be sufficient to consider only the Debye equation and, in particular, its limiting form at very low temperamres ... 

Although the tables presented by Parks and Huffman [1] are based on older data, they are often more convenient to use, because they are simpler and because they have been worked out for the liquid and the solid states as well as for the gaseous phase. A complete survey and analysis of methods of estimating thermodynamic properties is available in Janz s monograph [5], and in the work by Reid et al. [6]. Thermodynamicists should have a general acquaintance with more than one method of estimating entropies so they can choose the best method for a particular application. 

There is no evidence of any transition metal tetrafluoride being tetra-hedrally coordinated in the solid state, however. Thus the tetrafluorides are much less volatile than the hexafluorides are. Euler and Westrum 99) conclude from thermodynamic data on Tip4 that this compound is intermediary between molecular CF4 and 8-coordinated Zrp4. 

Condensation theory is based on thermodynamic equilibrium. More than a century s worth of experiments have yielded thermodynamic data (entropy and enthalpy of formation, plus heat capacity) for elements and compounds. Equations of state describing the stabilities of different compounds under various conditions can be calculated from these data, as briefly described in Box 7.1. Because liquids are not normally stable at the low pressures appropriate for space, the compounds in condensation calculations are generally solid minerals, but liquids can exist at higher pressures (achievable if areas of the nebula with enhanced dust concentrations relative to gas were vaporized). 

Methanol and Water. Methanol and water mixtures have been a popular choice for workers interested in free energies of transfer of ions from water into a mixed solvent. Such mixtures exhibit a drop in dielectric constant with increasing methanol content. Hence the electrical term must be estimated in order to compare spectroscopic and thermodynamic quantities. Feakins and Voice (28) have presented new data and revised earlier data for the alkali metal chlorides. In advance of carefully determined and extrapolated emf data for fluorides, using the solid state fluoride selective electrode based on lanthanum fluoride, some data of moderate accuracy have been presented (27). On the... 

For the convenience of tabulation and compulation of thermodynamic data, it is essential lo present them in a commonly accepted form relative to a single standard slate of reference. At all lemperatures, the standard stale for a pure liquid or solid is the condensed phase under a pressure of I atmosphere. The standard stale for a gas is the hypothetical ideal gas at anil fugarity (equivalent til a perfect gas" stale), in which state the enthalpy is that of the real gas at the same temperature when the pressure approaches aero. Values of thermodynamic quantities for standard-state conditions are identified by a superscriptQ. and Hn. for instance, is the enthalpy change of a reaction when reactants and products are in the standard state. 

---