Enthalpy dissolution

KEY TERMS endothermic reaction enthalpy of reaction dissolution enthalpy of formation... 

Enthalpy of dissolution is the enthalpy connected with the dissolution of the given solution it depends on the composition and can be calculated from the integral dissolution enthalpies of solutions in the final and starting states ... 

Utilization of the dissolution enthalpies in Eq. (4.36) is justified when the individual phases are adequately diluted in an amount of the chosen solvent. With regard to the error in the solution calorimetry, the enthalpy of mixing and the enthalpy of dissolution could be neglected only when the amount of the solvent in the solution formed has not changed. 

The first extrapolation by a square root of concentration in Zr seems to be incorrect, because the ionic strength in these solutions is not affected by the concentration of Zr but by that of the background electrolyte. At constant ionic strength, the dissolution enthalpy should be independent of the Zr concentration. The observed concentration dependeney may indicate a change in solution speciation, hence polymer formation may have occurred. The inclusion of the data of the authors in the overall assessment of Zr hydrolysis requires a re-interpretation of their experimental data in terms of mono-mer/polymer transition. Polymer formation in similar solutions was analysed by [75TRI/SCH]. A re-interpretation was found to be important in similar solutions [75TRI/SCH] (see Appendix A entry) aceording to the reaction ... 

Solubility measurements are especially valuable for the determination of an internally consistent set of thermodynamic data for nickel carbonates. Other methods turned out to be less convenient. Thus the calorimetric determination of the dissolution enthalpy according to Reaction (V.106) is bound to be inaccurate, because the result depends to a high extent on the state of carbon dioxide. It is well known that keeping CO2 quantitatively either in solution or in the gas phase is quite difficult. 

The peritectic temperature Tp is established by bends in the slope of the solubility curve since an equilibrium solid phase and its dissolution enthalpy are different below and above Tp. 

Fig. 7. Dependencies of thermal (peritectic decomposition temperature) and thermodynamic (dissolution enthalpy) stability of R123 lattices upon their geometrical stability, calculated using ionic radii of R (top...

The respective values of Ep and Ep p calculated from Fig.5 are about 4.8 Kcal/mole and 2.3 l cal/mole respectively the low activation energy of the isothermal process being indicative of a viscous flow mechanism while.the relatively higher value of Ep j is comparable with those generally found in diffusive processes (17-19). The concept of apparent activation energies for transport in a temperature gradient arises from the different dissolution enthalpies of the permeant on opposite partition sides. From the definition of enthalpy it follows that... 

Equation (4) represents an overall energetic balance through which it is possible to assess that the value of the sum of dissolution enthalpies is rather small, while nothing can be said about their individual values. 

If we know an activity coefficient at a certain temperature, it is possible to obtain the value for another temperature, knowing the dissolution enthalpy of the component as a function of the composition and the temperature. 

Determination of the amount of paraffin, i.e. the crystallizable fraction (CF), on the heating of DF, requires the use of the equation AHdiss = f(T°C). The way this equation is established is explained elsewhere [5, 8], This relation between the paraffin dissolution enthalpy and temperature should of course be reviewed when paraffins and FAME precipitate together. For the latter, a new equation needs to be assessed. 

Figure 2.7 Comparison between measured and calculated heat flows of a portland cement hydrated at 23°C using a w/c of 0.50. Heat flow was calculated from quantitative XRD anaiyses using the dissolution enthalpies of the clinker phases and the precipitation enthalpies of the hydrate phases. (From Jansen, D. et al., Cement and Concrete Research, 42(1), 134-138, 2012a. With permission.)...

It is worth mentioning that to obtain reliable interatomic potentials, the energies resulting from the application of the EAM have been parameterized by fitting available experimental data, such as elastic constants, dissolution enthalpies of binary alloys, bulk lattice constants, and sublimation heats."... 

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