Revised values for the Gibbs free energy of formation of [Al(OH) 4 aq - ], diaspore, boehmite and bayerite at 298.15 K and 1 bar, the thermodynamic properties of kaolinite to 800 K and 1 bar, and the heats of solution of several gibbsite samples

Details Revised values for the Gibbs free energy of formation of [Al(OH) 4 aq - ], diaspore, boehmite and bayerite at 298.15 K and 1 bar, the thermodynamic properties of kaolinite to 800 K and 1 bar, and the heats of solution of several gibbsite samples Revised values for the Gibbs free energy of formation of [Al(OH) 4 aq - ], diaspore, boehmite and bayerite at 298.15 K and 1 bar, the thermodynamic properties of kaolinite to 800 K and 1 bar, and the heats of solution of several gibbsite samples

Oct 1978

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978gecoa..42.1533h&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 42, Issue 10, pp.1533-1543

Mathematics

Logic

3

Scientific paper

Solution calorimetric measurements compared with solubility determinations from the literature for the same samples of gibbsite have provided a direct thermochemical cycle through which the Gibbs free energy of formation of [Al(OH) 4 aq - ] can be determined. The Gibbs free energy of formation of [Al(OH) 4 aq - ] at 298.15 K is -1305 ± 1 kJ/mol. These heat-of-solution results show no significant difference in the thermodynamic properties of gibbsite particles in the range from 50 to 0.05 m. The Gibbs free energies of formation at 298.15 K and 1 bar pressure of diaspore, boehmite and bayerite are -9210 ± 5.0, -918.4 ± 2.1 and -1153 ± 2 kJ/mol based upon the Gibbs free energy of [A1(OH) 4 aq - ] calculated in this paper and the acceptance of -1582.2 ± 1.3 and -1154.9 ± 1.2 kJ/mol for the Gibbs free energy of formation of corundum and gibbsite, respectively. Values for the Gibbs free energy formation of [Al(OH) 2 aq + ] and [AlO 2 aq - ] were also calculated as -914.2 ± 2.1 and -830.9 ± 2.1 kJ/mol, respectively. The use of [AlC 2 aq - ] as a chemical species is discouraged. A revised Gibbs free energy of formation for [H 4 SiO 4aq 0 ] was recalculated from calorimetric data yielding a value of -1307.5 ± 1.7 kJ/mol which is in good agreement with the results obtained from several solubility studies. Smoothed values for the thermodynamic functions C P 0 , ( H T 0 - H 298 0 )/ T , ( G T 0 - H 298 0 )/ T , S T 0 - S 0 0 , H f ,298 0 kaolinite are listed at integral temperatures between 298.15 and 800 K. The heat capacity of kaolinite at temperatures between 250 and 800 K may be calculated from the following equation: C P 0 = 1430.26 - 0.78850 T + 3.0340 × 10 -4 T 2 -1.85158 × 10 -4 T 2 . The thermodynamic properties of most of the geologically important Al-bearing phases have been referenced to the same reference state for Al, namely gibbsite.

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Revised values for the Gibbs free energy of formation of [Al(OH) 4 aq - ], diaspore, boehmite and bayerite at 298.15 K and 1 bar, the thermodynamic properties of kaolinite to 800 K and 1 bar, and the heats of solution of several gibbsite samples does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

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