Sulfate stability constants, enthalpies

Stability Constants, Enthalpies, and Entropies of Plutonium(III) and Plutonium(IV) Sulfate Complexes... 

Stability constants, enthalpies, and entropies have been published for both the 1 1 and 1 2 sulfate complexes of the Th1 "1"... 

Nash, K. L. Cleveland, J. M. Stability Constants, Enthalpies, and Entropies of Plutonium(III) and PlutoniumfTV) Sulfate Complexes. In Plutonium Chemistry Carnall, W. T., Choppis, G. R., Eds. American Chemical Society Washington, DC 1983, Vol. 216, pp 251-262. 

DeCarvalho and Choppin (10, 11) previously have reported the stability constants, complexation enthalpies, and entropies for a series of trivalent lanthanide and actinide sulfates. As their work was conducted a pH 3, the dominant sulfate species was S0 and the measured reaction was as in equation 12. 

Walker et al. (2007) developed 6 QSARs to predict the toxicity of 17 cations to sunflower seeds (F.l. Helianthus annuus Sunspot) from the metal s physical properties and natural occurrence levels (Table 5.4). The QSARs predicted EC50 values based on the cation concentration producing a 50% inhibition of radicle growth one day after emergence. The QSAR developed with density of the elements (p), enthalpy of formation of metal sulfides (AHJ, and the stability constants of metal ions with sulfate (log Ki [sulphate]) produced the highest adjusted (Table 5.20). For natural occurrence levels, the QSAR developed with metal concentrations in soil (log Msoi,), the median elemental composition of soils (mg X/kg soil), and the calculated mean of the elemental content in land plants (Land Plants) produced the highest adjusted... 

Observed stability constants of metal ion-acetato complexes Calculated constant of metal ion complexes with NH3 Enthalpy of formation of sulfides Stability constant of metal ion complexes with sulfate Average molar metal concentration in soil at 10% moisture Medians of elemental composition of soils Calculated mean of the elemental content in land plants Intrinsic (van der Waals) molecular volume... 

In contrast to the situation observed in the trivalent lanthanide and actinide sulfates, the enthalpies and entropies of complexation for the 1 1 complexes are not constant across this series of tetravalent actinide sulfates. In order to compare these results, the thermodynamic parameters for the reaction between the tetravalent actinide ions and HSOIJ were corrected for the ionization of HSOi as was done above in the discussion of the trivalent complexes. The corrected results are tabulated in Table V. The enthalpies are found to vary from +9.8 to+41.7 kj/m and the entropies from +101 to +213 J/m°K. Both the enthalpy and entropy increase from ll1 "1" to Pu1 with the ThSOfj parameters being similar to those of NpS0 +. Complex stability is derived from a very favorable entropy contribution implying (not surprisingly) that these complexes are inner sphere in nature. 

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