Platinum thermodynamic propertie

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. 

The promoting effects of the various metals can be explained by their electronic interactions with the platinum. Many attempts have been made to find correlations between the catalytic performance and thermodynamic properties of different metals (ref. 6). One such correlation is... 

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

The third largest class of enzymes is the oxidoreductases, which transfer electrons. Oxidoreductase reactions are different from other reactions in that they can be divided into two or more half reactions. Usually there are only two half reactions, but the methane monooxygenase reaction can be divided into three "half reactions." Each chemical half reaction makes an independent contribution to the equilibrium constant E for a chemical redox reaction. For chemical reactions the standard reduction potentials ° can be determined for half reactions by using electrochemical cells, and these measurements have provided most of the information on standard chemical thermodynamic properties of ions. This research has been restricted to rather simple reactions for which electrode reactions are reversible on platinized platinum or other metal electrodes. 

Although one of the more complex electrochemical techniques [1], cyclic voltammetry is very frequently used because it offers a wealth of experimental information and insights into both the kinetic and thermodynamic details of many chemical systems [2], Excellent review articles [3] and textbooks partially [4] or entirely [2, 5] dedicated to the fundamental aspects and apphcations of cyclic voltammetry have appeared. Because of significant advances in the theoretical understanding of the technique today, even complex chemical systems such as electrodes modified with film or particulate deposits may be studied quantitatively by cyclic voltammetry. In early electrochemical work, measurements were usually undertaken under equilibrium conditions (potentiometry) [6] where extremely accurate measurements of thermodynamic properties are possible. However, it was soon realised that the time dependence of signals can provide useful kinetic data [7]. Many early voltammet-ric studies were conducted on solid electrodes made from metals such as gold or platinum. However, the complexity of the chemical processes at the interface between solid metals and aqueous electrolytes inhibited the rapid development of novel transient methods. 

Table 1 summarizes some of the most relevant results from thermodynamic studies on platinum single-crystal surfaces. In order to facilitate the comparison of thermodynamic data corresponding to different adsorption reactions, values of the thermodynamic properties at the standard state ( AG , A/T and AS ) are provided. Values of the lateral interaction parameter (a>), and its temperature dependence (dm/dT) are also given in Table 1. While the lateral interaction parameter measures the magnitude of the lateral interactions, its temperature dependence reflects the entropic contributions to the lateral interactions. Therefore, the enthalpic contribution to the lateral interaction energy, can be obtained from - T da/dT.

Due to the thermodynamic properties of platinum, which can be seen in the potential-pH diagram, the dissolution of Pt can follow two different reaction paths under fuel cell conditions, which is either the direct dissolution of the metal ... 

The purpose of this chapter is to explore the properties and reactions of various Pt-nucleobase complexes. After a short description of various binding modes, attention will be paid on the effects of coordinated platinum. Topics include, e.g., isomerization, thermodynamic stability, and solvolyt-ic reactions of Pt-nucleobase complexes. Finally, factors affecting the mechanism and kinetics of substitution reactions by various nucleophiles will be discussed. 

Reactions of cisplatin and its hydrolytes with longer-chain amino acids +NH3(CH2)nC02 are less relevant to the biological properties of platinum because these compounds are less abundant in vivo. The six- and seven-membered chelate rings formed with /3-alanine (n = 2) and y-aminobutyric acid (n = 3) are progressively less stable kinetically and thermodynamically than the five-membered A/, 0-chelate ring formed with glycine [3]. 

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