ENTHALPY CHANGES FOR COPOLYMER SOLUTIONS

2010 ◽  
pp. 359-378
Keyword(s):  
Enthalpy Changes

Inerte Amminkomplexe als mehrwertige Kationsäuren in wäßriger Lösung / Inert Ammine Complexes as Multivalent Cationic Acids in Aqueous Solution

1980 ◽  
Vol 35 (9) ◽  
pp. 1096-1103 ◽  
Author(s):  
Matthias Kretschmer ◽  
Lutwin Labouvie ◽  
Karl-W. Quirin ◽  
Helmut Wiehn ◽  
Ludwig Heck
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Spectrophotometric Method ◽  
Complex Cation ◽  
Aqua Ligand ◽  
Second Step ◽  
Acidity Constants ◽  
Ammine Complexes ◽  
Temperature Variations ◽  
Enthalpy Changes

Acidity constants of ammine complexes of tetravalent platinum in aqueous solutions have been determined by a spectrophotometric method at very low ionic strengths and extrapolated to zero ionic strength. Temperature variations of pK-values (25 °C and 50 °C) yield thermodynamic parameters for two successive deprotonation steps of hexaammineplatinum(IV), pentaamminechloroplatinum(IV), and tris(ethylenediamine)pla- tinum(IV) complexes and for the deprotonation of pentaammineaquacobalt(III) ion.The enthalpy changes for the first and second steps are similar and range from 50 to 75 kJ/mole while for the aqua ligand of Co(III) 33 kJ/mole are found. The very large dif­ference in the entropy changes (about 70 to 80 J/K mole for the first step and -10 to + 20 J/K mole for the second step) is interpreted by a model of solvation change. The primary hydration sphere of strongly oriented and immobilized water dipoles around the highly charged complex cation is transformed to a hydrogen-bonded solvation sheath when the electric field of the complex is weakened upon release of the first proton.

Thermodynamics of In Situ Formation of Mg2Si and MgO in AZ91D /Flyash Composites

2011 ◽  
Vol 686 ◽  
pp. 378-381
Author(s):  
Si Rong Yu ◽  
Zhi Qiu Huang ◽  
Jia An Liu
Keyword(s):  
Fly Ash ◽  
Thermodynamic Calculation ◽  
Interfacial Reactions ◽  
Mg Alloy ◽  
Free Enthalpy ◽  
Alloy Matrix ◽  
Microstructure Observation ◽  
Enthalpy Changes ◽  
Fly Ash Cenospheres

Novel AZ91D Mg alloy/fly-ash cenospheres (AZ91D/FAC) composites were fabricated by melt stir technique. The thermodynamic analyses of the interfacial reactions, the microstructure observation, and the phase analyses of the AZ91D/FAC composites were investigated. The results showed that the cenospheres were almost filled with Mg alloy matrix. In-situ MgO and Mg2Si phases were formed in Mg alloy matrix and near the interfaces between the cenospheres and Mg alloy matrix. Through the thermodynamic calculation, it can be found that the standard free enthalpy changes of these interfacial reactions are all negative at the temperature of Mg alloy melt preparation in this work, and these reactions can occur.

Molten fatty acid salts as model ionic liquids. I. Thermodynamic and transport parameters of some organic sodium salts

1971 ◽  
Vol 322 (1550) ◽  
pp. 281-299 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Transport Parameters ◽  
Sodium Propionate ◽  
Isotropic Liquid ◽  
Enthalpy Changes ◽  
Physical Measurements ◽  
Ionic Melts ◽  
Ionic Solids ◽  
Steep Decrease ◽  
Transition Points

Procedures are described for maintaining good chemical stability in molten alkali-metal carboxylates, up to about 350 °C. Valid physical measurements can be made and the fluids can be used up to about this temperature, above which spontaneous decomposition of the anions is difficult to repress. Molten sodium propionate has a useful liquid range of about 60 °C and sodium isobutyrate of about 90 °C. Sodium n -butyrate transforms into a ‘liquid crystal’ at about 250 °0 and into the isotropic liquid at 324 °C. For sodium isovalerate corresponding transition points are respectively 188 and 280 °C. Thermodynamic measurements are reported of volume and enthalpy changes at transition and melting points. Transport parameters measured include the viscosity and the electrical conductivity. The viscosity of these ionic melts undergoes a steep decrease at the transition from mesomorphic to isotropic liquids. Jumps in ionic conductivity are found both at the melting and clearing points. Even for the isotropic liquids, the ratio of viscosity to electrical conductivity is exceptionally high, compared with the other ionic melts. Mechanisms of melting for these ionic solids are discussed.

COMPUTING NARROW NANOTUBES AND THEIR DERIVATIVES

2002 ◽  
Vol 01 (03n04) ◽  
pp. 303-312 ◽  
Author(s):  
ZDENĚK SLANINA ◽  
FILIP UHLÍK ◽  
LESZEK STOBINSKI ◽  
HONG-MING LIN ◽  
LUDWIK ADAMOWICZ
Keyword(s):  
Computational Study ◽  
Activation Barriers ◽  
Enthalpy Changes ◽  
Oxygen Addition

Very recently, narrow nanotubes have been observed with diameters of 5 or even 4 Å. In this report we survey calculations that have so far been performed on narrow model nanotubes, namely capped by fragments of D2d and D6h C 36 fullerene cages or by fragments of C 32 and C 16quasi-fullerene cages with two four-membered rings, or finally by a fragment of dodecahedral C 20. The computations can reproduce the observed diameters of the narrow nanotubes. The results also indicate that fragments of C 32, used as caps instead of C 36, can lead to quite competitive energetics. Thus, a novel possibility that some of the narrow nanotubes can contain four-membered rings at their tips seems plausible. The present paper also surveys computational study of oxygen additions to the narrow nanotubes, i.e., a problem frequently studied with fullerenes. Both thermodynamic enthalpy changes and kinetic activation barriers for oxygen addition to selected bonds are computed and analyzed. The lowest isomer (thermodynamically the most stable) is never of the 6/6 type, i.e., the thermodynamically most convenient structures are produced by oxygen additions to the nanotube tips. The computations show that narrow nanotubes should be relatively prone to additions of oxygen.

scholarly journals ANALISIS KONDISI RESERVOIR PANAS BUMI DENGAN MENGGUNAKAN DATA GEOKIMIA DAN MONITORING PRODUKSI SUMUR ELS-02 LAPANGAN ELSA

PETRO ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 194
Author(s):  
Nabilla Elsaphira Putri ◽  
Onnie Ridaliani ◽  
Widia Yanti
Keyword(s):  
Chloride Concentration ◽  
Reservoir Management ◽  
Calcium Sulphate ◽  
Geothermal Field ◽  
Carbonate Concentration ◽  
Enthalpy Changes ◽  
Geothermal Fluids ◽  
Time Problem ◽  
Concentration Changes

<p><em>A</em><em> good reservoir management is needed </em><em>to maintain</em><em> the </em><em>availability and </em><em>quality of geothermal production fluid. When producing geothermal fluids, there are some changes in reservoir parameters such as declining of reservoir pressure and temperature, chemical composition of geothermal fluids, </em><em>and </em><em>states of fluid that would affect the quality of reservoir by mixing, boiling, or cooling processes that may be happened </em><em>because of</em><em> those changes. </em><em>It is</em><em> becoming a concern on reservoir management. In this case, chemical </em><em>concentrations </em><em>of fluid</em><em>s</em><em> monitoring is one of methods that can perform to reach a well reservoir management of geothermal field. With </em><em>chemical </em><em>monitoring process, current reservoir condition and processes </em><em>that </em><em>occurred during exploitation can be defined</em><em>. In ELS-02 by monitoring and analyzing its enthalpy changes, chloride concentration changes, and NCG concentration changes and supported by its calcium, sulphate, and carbonate concentration profile, two processes could be defined:</em><em> </em><em>mixing with </em><em>surface </em><em>cooler water and reinjection breakthrough.</em><em> </em><em>Other than that, casing leak that causing surface water enter the well could be detected.  </em><em>These become a sign to reservoir engineer to prepare for problems that may occur in near time </em><em>term </em><em>relating to well problem </em><em>such as scaling </em><em>and long time problem like massive cooling or drying of reservoir. After all, further development scenario of Elsa field can be made to improve its performance in producing fluids and heats. </em></p><p> </p>

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