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Kinetics of the formation and hydrolysis reactions of some thiomolybdate(VI) anions in aqueous solution
Affiliation:1. Department of Mechanical Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece;2. Dipartimento di Scienze & Tecnologie Aerospaziali, Politecnico di Milano, Via La Masa, 34, 20156 Milano, Italy;3. DIENCA, Università degli Studi di Bologna, Via Risorgimento 2, 40136 Bologna, Italy;1. Géobiosphère Actuelle & Primitive, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, F-75005 Paris, France;2. Swedish Museum of Natural History, Box 50007, SE104-05 Stockholm, Sweden;3. Geological Survey of Norway, Leiv Eirikssons vei 39, 7491 Trondheim, Norway;4. Tallinn University of Technology, Institute of Geology, 19086 Tallinn, Estonia;5. Centre for Arctic Gas Hydrate, Environment and Climate, University of Tromsø, 9037 Tromsø, Norway;1. National Research Tomsk Polytechnic University, Tomsk, Russia;2. Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk, Russia;1. Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99352, United States;2. Idaho National Laboratory, 2525 Fremont Ave, Idaho Falls, ID 83415, United States;1. Institute of Materials, Shanghai University, Shanghai 200072, PR China;2. Laboratory for Microstructures, Shanghai University, Shanghai 200444, PR China
Abstract:The kinetics of the formation of the thiomolybdate ions MoOS32− and MoS42− were determined spectroscopically from the addition of excess sulphide to MoO2S22− in pH buffered media (6–8) at 30 °C. The reverse (hydrolysis) reactions of MoO2S22− and MoOS32− were measured under the same conditions. The reaction rates measured are shown below:
></figure> Values of the rate-constants (s<sup>−1</sup>) obtained at pH 7.0 were <em>k</em><sub>10</sub> 2.4 × 10<sup>−3</sup>, <em>k</em><sub>21</sub> 1.5 × 10<sup>−5</sup>, <em>k</em><sub>30</sub> 2.1 × 10<sup>−5</sup>, <em>k</em><sub>23</sub> 6.0 × 10<sup>−4</sup>, and <em>k</em><sub>34</sub> 1.9 × 10<sup>−5</sup>; where the results are comparable they are in good agreement with those obtained by earlier workers, although different conditions were used. However, in this work it was found that certain reactions had to be mathematically treated as two consecutively occurring reactions. There is also a difference in interpretation of the mechanism of the hydrolysis reactions of the tri- and tetrathio ions. In general the lability towards further S replacement of O atoms, and the reverse reaction, decreased with increased S substitution. All reaction rates increased with increasing <strong>H<sup>+</sup></strong> ion concentration, mostly this was a linear relationship over the limited pH range examined. The effect of the <strong>H<sup>+</sup></strong> ion is interpreted in terms of protonation of the oxythiomolybdate ions at an O atom leading to increased lability.</td>
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