ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7

Published monthly
 

On the applicability and predictive power of additive equations in the evaluation of standard enthalpies of formation of crystallohydrate salts of rare-earths and actinoides

N.I. Yanakiev

Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, B-1040 Sofia

 

Abstract: The validity of equations for the additive evaluation of the standard enthalpies of formation (∆Hf°) of crystallohydrates of rare-earth elements and actinoides is established on the basis of experimental data. Rozenfeld's equation, i.e.  ∆Hf°crystallohydrate) =  ∆Hf° (anhydrous salt) + b1 N where N is the hydration value and b1 is the increment for one water molecule, shows the best approximation to the experimental data and offers the best predictive possibilities. For N = b1 is —307.5 kJ mol-1 , for each from the second to the sixth water molecule bx is — 300.4 kJ mol-1, while for any water molecule belonging to the second coordination sphere bx is — 292.9 kJ mol-1 . The present considerations corroborate the previously published conclusion that the experimentally obtained AHf values for crys­talline phosphate dihydrates of 12 rare-earth elements should be recon­sidered. The use of a general increment of low value ( — 297.1 k J mol-1 ) is shown to be one of the causes for considering in the literature some∆Hf° of crystallohydrates as subject to nonlinear changes and lack of additivity. Rozenfeld's equation is also shown to be useful in the rapid check of crystallohydrate ∆Hf° values in the cases where they do not agree with experimental data for other crystallohydrates of the same salt.

Full paper in Portable Document Format: 416a731.pdf

 

Chemical Papers 41 (6) 731–738 (1987)

Saturday, October 23, 2021

IMPACT FACTOR 2020
2.097
SCImago Journal Rank 2020
0.344
SEARCH
Advanced
VOLUMES
XXVIII. International Conference on Coordination and Bioinorganic Chemistry
© 2021 Chemical Papers