| Abstract: | Equilibrium aqueous hydrogen concentration and corresponding energies of reaction, ??Grxno(T, P), for the reaction Co(s) + H2O(l) = CoO(s) + H2(aq) have been determined at temperatures between 256 and 355 ??C and at 400 bar. Steady-state concentrations of hydrogen were approached in experiments under conditions of both H2 excess and deficiency containing the solids Co, CoO and liquid water. All experiments were carried out in flexible gold and titanium reactors with the capability of on-line fluid sampling. Measured equilibrium molal concentrations of H2(aq) at 256, 274, 300, 324 and 355 ??C are 0.81(?? 0.01) ?? 10- 3 1.11(?? 0.01) ?? 10- 3, 1.92(?? 0.01) ?? 10- 3, 3.71(?? 0.06) ?? 10- 3, 7.54(?? 0.12) ?? 10- 3, respectively, and corresponding values of ??Grxno(T, P) in units kJ ?? mol- 1 are 31.4(?? 0.1), 31.0(?? 0.1), 29.8(?? 0.1), 27.7(?? 0.5) and 25.5(?? 0.9), respectively. Using published heat capacity data for Co(s) and CoO(s) and - 79.6 J ?? mol- 1 ?? K- 1 for the entropy of formation of CoO we calculated for this study a value for ??GCoO,Tr,Pro = - 214.5(?? 0.9) kJ ?? mol- 1 and ??HCoO,Tr,Pro = - 238.3(?? 0.9) kJ ?? mol- 1 at 25 ??C and 1 bar. The value of ??HCoO,Tr,Pro determined in this study compares well with the reported calorimetric value of - 238.9(?? 1.2) kJ ?? mol- 1 [Boyle, B.J., King, E.G., Conway, K.C., 1954. Heats of formation of nickel and cobalt oxides (NiO and CoO) by combustion calorimetry. Journal of the American Chemical Society, 76, 3835-3837]. ?? 2008 Elsevier B.V. All rights reserved. |
| Genre: | Article |
| ProdID: | 70033085 |
| Citation Author: | Lemke, K. H.; Rosenbauer, R. J.; Bischoff, J. L.; Bird, D. K. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 144 |
| Citation Issue: | 3-4 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Chemical Geology |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 9 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | An hydrothermal experimental study of the cobalt-cobalt oxide redox buffer; 2008; Article; Journal; Chemical Geology; Lemke, K. H.; Rosenbauer, R. J.; Bischoff, J. L.; Bird, D. K. |
| Citation Start Page: | 136 |
| Citation Volume: | 252 |
| Citation Year: | 2008 |
| Type: | citation/reference |
| Text: | An hydrothermal experimental study of the cobalt-cobalt oxide redox buffer; 2008; Article; Journal; Chemical Geology; Lemke, K. H.; Rosenbauer, R. J.; Bischoff, J. L.; Bird, D. K. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1016/j.chemgeo.2008.02.005 |
| Date Other: | Tue, 1 Jan 2008 00:00 -0600 |
| Publisher: | |
