Thermochemical Study of Reduction and Oxidation Reactions of Molybdovanadophosphoric Heteropolyacids in Aqueous Solutions Full article
Journal |
European Journal of Inorganic Chemistry
ISSN: 1434-1948 , E-ISSN: 1099-0682 |
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Output data | Year: 1999, Number: 6, Pages: 1009-1014 Pages count : 6 DOI: 10.1002/(SICI)1099-0682(199906)1999:6<1009::AID-EJIC1009>3.0.CO;2-B | ||
Tags | Heteropolyacids, Hydrazine hydrate, Molybdovanadophosphates, Oxidations, Reduction, Thermochemistry | ||
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Abstract:
Differential enthalpies of reduction, –ΔrH4j, have been found at 343 K for 0.2 m aqueous heteropolyacids H3+xPVxMo12–xO40 (HPA-x, where 1 ≤ x ≤ 6) and their salts by hydrazine hydrate (HH). The –ΔrH4j values depend on x and m, where m = [VIV]/[HPA-x]. At m ≈ 0, the initial –ΔrH4j value is 436 ± 14 kJ mol−1 HH for all HPA-x. For HPA-x with 3 ≤ x ≤ 6, the curves –ΔrH4j = f(mj) have maxima associated with formation and reduction of the outer-sphere cation VVVIVO33+. A similar maximum is observed on reduction of 0.1 M VO2ClO4 in 4 M HClO4. No maxima are observed for the reduction of HPA-1, HPA-2, and salts of HPA-3. For HPA-3 salts, –ΔrH4j = f(mj) depends primarily on the pH of the salt solution, rather than on the nature of the cation. Reduction and oxidation of HPA-x and their salts are reversible reactions. In HPA-x solutions, VO2+ in the outer sphere is reduced first, and VV in the inner coordination sphere of the heteropoly anion is reduced next. Differential enthalpies for the oxidation of the reduced HPA-x by dioxygen (–ΔrH2j) have been calculated. The sequence of the oxidation of different VIV forms in the reduced HmHPA-x solutions is the reverse of that for the reduction of the VV forms in the initial HPA-x solutions.
Cite:
Zhizhina E.G.
, Odyakov V.F.
, Matveev K.I.
Thermochemical Study of Reduction and Oxidation Reactions of Molybdovanadophosphoric Heteropolyacids in Aqueous Solutions
European Journal of Inorganic Chemistry. 1999. N6. P.1009-1014. DOI: 10.1002/(SICI)1099-0682(199906)1999:6<1009::AID-EJIC1009>3.0.CO;2-B WOS Scopus РИНЦ
Thermochemical Study of Reduction and Oxidation Reactions of Molybdovanadophosphoric Heteropolyacids in Aqueous Solutions
European Journal of Inorganic Chemistry. 1999. N6. P.1009-1014. DOI: 10.1002/(SICI)1099-0682(199906)1999:6<1009::AID-EJIC1009>3.0.CO;2-B WOS Scopus РИНЦ
Dates:
Submitted: | Jul 10, 1998 |
Published online: | May 17, 1999 |
Published print: | Jun 1, 1999 |
Identifiers:
Web of science | WOS:000080432200013 |
Scopus | 2-s2.0-0032801216 |
Elibrary | 13330827 |
Chemical Abstracts | 1999:337304 |
Chemical Abstracts (print) | 131:50108 |
OpenAlex | W1991078104 , W4242483030 |