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Evaluation of thermodynamic functions relative to cavity formation in aqueous solutions

Comparison of the results calculated from Scaled Particle Theory and Sinanoglu's theory for 2-alkyl-9-methyladenines

Journal of Thermal Analysis and Calorimetry
Authors: W. Zielenkiewicz, P. Zielenkiewicz, and P. Lapshov

Abstract  

The results of calculation of free Gibbs energy and enthalpy of cavity formation were described using the Scaled Particle and Sinanoglu's theories.

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Abstract  

In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C p of phenylated polyphenylene and initial comonomer 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene was studied between 6 and 340 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield their energies of combustion DUcomb were measured. From the experimental data, the thermodynamic functions C p 0 (T), H 0(T)-H 0(0), S 0(T)-S0(0), G 0(T)-H 0(0) were calculated from 0 to 340 K, and standard enthalpies of combustion ΔH comb 0 and thermodynamic parameters of formation-enthalpies ΔH f 0, entropies ΔH f 0, Gibbs functions ΔG f 0 - of the substances studied were estimated at T=298.15 K at standard pressure. The results were used to calculate the thermodynamic characteristics (ΔH f 0S f 0, ΔG f 0) of phenylated polyphenylene synthesis in the range from 0 to 340 K.

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Abstract  

The ammonium manganese phosphate monohydrate (NH4MnPO4 · H2O) was found to decompose in three steps in the sequence of: deammination, dehydration and polycondensation. At the end of each step, the consecutive one started before the previous step was finished. The thermal final product was found to be Mn2P2O7 according to the characterization by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy. Vibrational frequencies of breaking bonds in three stages were estimated from the isokinetic parameters and found to agree with the observed FTIR spectra. The kinetics of thermal decomposition of this compound under non-isothermal conditions was studied by Kissinger method. The calculated activation energies Ea are 110.77, 180.77 and 201.95 kJ mol−1 for the deammination, dehydration and polycondensation steps, respectively. Thermodynamic parameters for this compound were calculated through the kinetic parameters for the first time.

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Abstract  

The molar excess enthalpiesH E for the water +N-methyl-2-pyrrolidinone binary mixtures have been measured as functions of mole fraction at 298.15, 308.15 and 318.15 K, using isoperibol rotating calorimeter. A hydrogen bonding pairs model proposed by Luzar was fitted to the experimental dataH E,G E for the binary mixtures of water with hexamethylphosphoric triamide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidinone.

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Abstract  

The investigations carried out till now and presented in this paper show that apart from the well known itinerant properties of yttrium in respect to free energy of complex formation, also actinides(III) change their position in the lanthanide series in respect to G. It has also been shown that yttrium and actinides exhibit itinerant behaviour in respect to unit cell volumes. Evidence has been presented that delocalization of 4f and 5f orbitals is the reason for the two types of migratory properties. Since the itinerant behaviour of yttrium and actinides(III) in respect to stability constants (free energies of complex formation) is the basis for yttrium-lanthanides and lanthanides-actinides group separations, a better qualitative understanding of the mechanism involved may contribute to the development of more efficient separation procedures.

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Abstract  

The enthalpies, entropies and Gibbs energies of inclusion of dl-1,3-, 1,4- and meso-2,3-butanediols into α- and β-cyclodextrin cavities from ideal gas phase have been determined on the basis of newly obtained experimental data of the butanediols. The butanediol molecules are stabilised strongly in the cavities due to interactions with inner walls of the cavities. Entropies of the gaseous isomers are greatly decreased in the cavities. The largest decrease is obtained for the case of 2,3-BD. Discussions concerning the1,4-butanediol given in the preceding paper have been changed due to the adoption of new data on the butanediols.

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Abstract  

The position of Pu/III/ within lanthanides in respect to G0, H0 and S0 of complex formation with nitrate and thiocyanate ligands was determined by the extraction method. It was found that in respect to G0, Pu/III/ is a light pseudolanthanide for nitrate ligands and a heavy pseudolanthanide for thiocyanate ligands. A comparison of the positions of Pu/III/ and Am/III/ in respect to G0, H0 and S0 shows that the radius of plutonium is greater than that of americium in the An/NO3/ 5 2– complex and smaller in the An/NCS/3/TBP/n complex. The increase in the radii between plutonium and americium in the thiocyanate complex points out to a contribution from 5f orbitals to bonding.

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Abstract  

The thermodynamic characteristics of proton exchange in SO3H groups of a sulfonated network polymer based on cis-tetraphenylmetacyclophanoctol for Na+, Cu2+ cations from aqueous solutions were considered for the first time. Microcalorimetric measurements of the heat effects of Na+-H+ and Cu2+-H+ exchanges were performed, equilibrium compositions of polymer and solution were determined. The changes of Gibbs energy, enthalpy and entropy of ion exchange were calculated.

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Abstract  

Data on synthesis, thermal behavior and thermodynamic properties for the NZP phosphates NaMe2(PO4)3 and Na5Me(PO4)3 (Me=Ti, Zr, Hf) are reported. The compounds were synthesized by sol-gel method and solid-state reactions and characterized by X-ray powder diffraction, IR spectroscopy, electron microprobe and chemical analysis. Their thermal behavior was studied by the DTA measurements. The heat capacities of the phosphates were measured between temperatures 7 and 650 K. The fractal dimensions for the phosphates were calculated. The obtained thermodynamic characteristics of these phosphates and also literature data for the compounds of NZP type structure are summarized.

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