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Article: An hydrothermal experimental study of the cobalt-cobalt oxide redox buffer

TitleAn hydrothermal experimental study of the cobalt-cobalt oxide redox buffer
Authors
KeywordsCobalt
Cobalt oxide
Hydrogen
Hydrothermal
Redox buffer
Thermochemistry
Issue Date2008
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeo
Citation
Chemical Geology, 2008, v. 252 n. 3-4, p. 136-144 How to Cite?
AbstractEquilibrium aqueous hydrogen concentration and corresponding energies of reaction, ΔG rxn o(T, P), for the reaction Co (s) + H 2O (l) = CoO (s) + H 2(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 H 2 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 H 2(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 ΔG rxn o(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 ΔG CoO,Tr,Pr o = - 214.5(± 0.9) kJ · mol - 1 and ΔH CoO,Tr,Pr o = - 238.3(± 0.9) kJ · mol - 1 at 25 °C and 1 bar. The value of ΔH CoO,Tr,Pr o 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.
Persistent Identifierhttp://hdl.handle.net/10722/58709
ISSN
2015 Impact Factor: 3.482
2015 SCImago Journal Rankings: 2.346
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorLemke, KHen_HK
dc.contributor.authorRosenbauer, RJen_HK
dc.contributor.authorBischoff, JLen_HK
dc.contributor.authorBird, DKen_HK
dc.date.accessioned2010-05-31T03:35:25Z-
dc.date.available2010-05-31T03:35:25Z-
dc.date.issued2008en_HK
dc.identifier.citationChemical Geology, 2008, v. 252 n. 3-4, p. 136-144en_HK
dc.identifier.issn0009-2541en_HK
dc.identifier.urihttp://hdl.handle.net/10722/58709-
dc.description.abstractEquilibrium aqueous hydrogen concentration and corresponding energies of reaction, ΔG rxn o(T, P), for the reaction Co (s) + H 2O (l) = CoO (s) + H 2(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 H 2 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 H 2(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 ΔG rxn o(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 ΔG CoO,Tr,Pr o = - 214.5(± 0.9) kJ · mol - 1 and ΔH CoO,Tr,Pr o = - 238.3(± 0.9) kJ · mol - 1 at 25 °C and 1 bar. The value of ΔH CoO,Tr,Pr o 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.en_HK
dc.languageengen_HK
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeoen_HK
dc.relation.ispartofChemical Geologyen_HK
dc.subjectCobalten_HK
dc.subjectCobalt oxideen_HK
dc.subjectHydrogenen_HK
dc.subjectHydrothermalen_HK
dc.subjectRedox bufferen_HK
dc.subjectThermochemistryen_HK
dc.titleAn hydrothermal experimental study of the cobalt-cobalt oxide redox bufferen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0009-2541&volume=252&issue=3-4&spage=136&epage=144&date=2008&atitle=An+hydrothermal+experimental+study+of+the+cobalt-cobalt+oxide+redox+bufferen_HK
dc.identifier.emailLemke, KH:kono@hkucc.hku.hken_HK
dc.identifier.authorityLemke, KH=rp00729en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.chemgeo.2008.02.005en_HK
dc.identifier.scopuseid_2-s2.0-45449110581en_HK
dc.identifier.hkuros153264en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-45449110581&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume252en_HK
dc.identifier.issue3-4en_HK
dc.identifier.spage136en_HK
dc.identifier.epage144en_HK
dc.identifier.isiWOS:000257974500003-
dc.publisher.placeNetherlandsen_HK
dc.identifier.scopusauthoridLemke, KH=24168776600en_HK
dc.identifier.scopusauthoridRosenbauer, RJ=7003888851en_HK
dc.identifier.scopusauthoridBischoff, JL=7101715751en_HK
dc.identifier.scopusauthoridBird, DK=7201990536en_HK

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