The transpiration method was used to study the reaction of SiO2 (cristobalite) with water vapor. Measurements were made between T = (1073 and 1728) K with water vapor contents from (0.05 to 0.6) by volume fraction in argon. From the results, the thermodynamic parameters for Si(OH)4(g) and SiO(OH)2(g) were determined. At T = (1073 to 1373) K, Si(OH) 4 is the primary vapor species and second law measurements lead to ΔfH°(1200 K) = (-1344.6 ± 2.7) kJ • mol-1 and S°(1200 K) = (544.4 ± 2.1) J • mol-1 • K-1. Third law measurements lead to ΔfH°(298 K) = (-1351.3 ± 1.7) kJ • mol-1. These are in very good agreement with previous measurements and previous ab initio calculations. At T = (1673 and 1728) K, there is evidence of a second vapor species, SiO(OH)2(g). By subtracting the extrapolated Si(OH)4(g) pressure, it was possible to do a third law analysis and obtain a ΔfH°(298 K) for SiO(OH)2(g) of (-836 ± 40) kJ • mol-1. Previous measurements and ab initio calculations are within this range. © 2005 Elsevier Ltd. All rights reserved.
CITATION STYLE
Jacobson, N. S., Opila, E. J., Myers, D. L., & Copland, E. H. (2005). Thermodynamics of gas phase species in the Si-O-H system. Journal of Chemical Thermodynamics, 37(10), 1130–1137. https://doi.org/10.1016/j.jct.2005.02.001
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