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Estimation of the Standard Free Energy of Formation of Metal Arsenates, Selenates, and Selenites
Author(s) -
Essington M. E.
Publication year - 1988
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1988.03615995005200060010x
Subject(s) - selenate , arsenate , chemistry , metal , inorganic chemistry , selenium , aqueous solution , oxide , analytical chemistry (journal) , arsenic , chromatography , organic chemistry
An empirical method developed for estimating the standard free energy of formation (Δ G° f ) of solid phases is evaluated for metal arsenates, selenates, and selenites. A free energy function of a solid phase is found to be linearly correlated to a function of the metal oxide Δ G° f and the aqueous metal ion Δ G° f for the compound groups examined. The values estimated by this method are, on average, within ± 10.9, 10.4, and 12.0 kJ mol −1 of the experimental arsenate, selenate, and selenite values, respectively. A method for estimating the Δ G° f of hydrated metal arsenates and selenites is also evaluated. The estimated standard free energy of formation values of hydrated arsenates and selenites, on average, are within ± 23.7 and 10.0 kJ mol −1 , respectively, of the observed values. The error involved in estimating metal arsenate, selenate, and selenite Δ G° f values are comparable to those obtained when the estimation technique was applied to other compound types.