Showing papers on "Standard molar entropy published in 2009"
01 Feb 2009
TL;DR: The sorption kinetics and thermodynamics of 1,3-dinitrobenzene (DNB), m-nitrotoluene (mNT), p-nitrophenol (pNP), and nitrobenZene (NB) on as-grown and nitric acid-oxidized multiwalled carbon nanotubes (MWCNTs) suggested that the sorption of nitroaromatics (NACs) onto MWCNTs
Abstract: The sorption kinetics and thermodynamics of 1,3-dinitrobenzene (DNB), m-nitrotoluene (mNT), p-nitrophenol (pNP), and nitrobenzene (NB) on as-grown and nitric acid-oxidized multiwalled carbon nanotubes (MWCNTs) were investigated. The sorption kinetics was well described by a pseudo-second-order rate model, while both Langmuir and Freundlich models described the sorption isotherms well and the sorption thermodynamic parameters of equilibrium constant (K(0)), standard free energy (DeltaG), standard enthalpy (DeltaH), and standard entropy changes (DeltaS) were measured. The values of DeltaH and DeltaG suggested that the sorption of nitroaromatics (NACs) onto MWCNTs was exothermic and spontaneous. The structure, number, and position of nitro groups of NACs were the main factors affecting the sorption rate and capacity. Treatment of the MWCNTs with nitric acid increased both the surface area and the pore volume and introduced oxygen-containing functional groups to the MWCNTs, which depressed the sorption of NACs onto MWCNTs.
170 citations
TL;DR: The metal-binding property of chitosan is used to incorporate titanium metal and applied as an adsorbent for fluoride adsorption and a comparison of fluoride removal in simulated and field water shows a high adsorptive capacity in simulated water.
97 citations
TL;DR: In this article, the effects of initial lead ion concentration, contact time, pH and temperature on the removal of Pb(II) systematically were evaluated by applying the van-t Hoff equation, which describes the dependence of equilibrium constant on temperature.
65 citations
TL;DR: In this paper, it is shown that substitution of iron for molybdenum results in stabilization of a cubic quasi-perovskite locally inhomogeneous structure, which is evidenced by HREM and Moessbauer spectroscopy.
59 citations
TL;DR: Quantitative fluorescence analysis reveals that the micelle distribution in the biphasic system has a very strong temperature dependence, which is favorable for control of the transportation, and a detailed mechanism for the transfer is proposed.
Abstract: The micelle shuttle utilizing block copolymer micelles as nanocarriers for transportation between water and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), is examined in detail. Rhodamine B, a dye with a high molar absorptivity and fluorescence quantum yield, is conjugated to a short poly(1,2-butadiene) homopolymer and then loaded in amphiphilic poly((1,2-butadiene)-block-ethylene oxide) (PB−PEO) block copolymer micelles. The round-trip transportation of the micelles between water and the ionic liquid is simply triggered by temperature; it is fully reversible, quantitative, and without leakage. Quantitative fluorescence analysis reveals that the micelle distribution in the biphasic system has a very strong temperature dependence, which is favorable for control of the transportation. The standard Gibbs free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) of the micelle shuttle are extracted from the temperatur...
54 citations
TL;DR: In this paper, a solid-state electrochemical cell incorporating yttria-doped thoria (YDT) as the electrolyte and a mixture of (Mn + MnO) as a reference electrode was used for the formation of ditantalum pentoxide (Ta2O5) from Ta metal and diatomic oxygen gas.
45 citations
TL;DR: In this article, a defect model involving partial occupancy by oxide ions and hydroxide ions of the structural sintered disks has been modeled and discussed in terms of the defect model.
Abstract: Mayenite, Ca12Al14O33, has been synthesized by a citric acid route, with final sintering at 1200−1350 °C. Phase purity has been characterized by X-ray diffraction and scanning electron microscopy. The hydration has been investigated under oxidizing and reducing conditions using thermogravimetry versus T and pH2O, as well as in situ H2O/D2O isotope exchange. The two data sets are in general correspondence and yield standard entropy and enthalpy changes of hydration (for 1 mol of H2O) of −123 ± 10 J/mol K and −240 ± 16 kJ/mol, respectively, in overall agreement with previous literature. The ac conductivity of sintered disks has been measured by the 4-point van der Pauw method versus pO2 at 900−1200 °C. It reflects mainly n-type electronic conductivity under reducing conditions and ionic (mainly oxide ion) conductivity under oxidizing conditions. The conductivity contributions are modeled and discussed in terms of a defect model involving partial occupancy by oxide ions and hydroxide ions of the structural s...
37 citations
TL;DR: In this article, the adsorption data of Gorbach et al. were re-analyzed and model isotherms were derived considering a two site hypothesis, one for α cage and one for β cage.
Abstract: The adsorption data of Gorbach et al. (Adsorption 10(1): 29–46, 2004) and Morris (J. Colloid Interface Sci. 28: 149–155, 1968) for the adsorption of water on 4A zeolite pellets is re-analyzed. Model isotherms are derived considering a two site hypothesis, one for the α cage and one for the β cage. Four simple model isotherms are fitted to the data. Both a dual site Toth or dual site Langmuir isotherm model fit the data adequately. The optimized standard enthalpy and entropy of adsorption parameters derived from the data are surprising for the β cage. The optimized standard enthalpy of the β cage is 1/3rd of that observed calorimetrically, and the standard entropy of adsorption is positive, a physical impossibility. Substituting the calorimetric enthalpy of adsorption corrected the standard differential entropy of sorption values resulting in the standard entropy of sorption values varying significantly with temperature. This variation is postulated to be due to either water of hydration formation, or clathrate formation, or the formation of clusters of water such as dimers, trimers, etc.
36 citations
TL;DR: In this paper, the heat capacity of the chlorite CCa-2 from Flagstaff Hill, California, was measured by low temperature adiabatic calorimetry and differential scanning caloreimetry, from 5 to 520 K (at 1 bar).
34 citations
TL;DR: In this paper, an ionic liquid (IL) HPReO4 (N-hexylpyridine rheniumate) was prepared and the density and surface tension of the IL were determined in the temperature range of (293.15 to 343.15) K.
Abstract: An ionic liquid (IL) HPReO4 (N-hexylpyridine rheniumate) was prepared. The density and surface tension of the IL were determined in the temperature range of (293.15 to 343.15) K. The ionic volume and surface entropy of the IL were estimated by extrapolation. In terms of Glasser’s theory, the standard molar entropy and lattice energy of the IL were estimated. Using Kabo’s method and Rebelo’s method, the molar enthalpy of vaporization of the IL, ΔlgHm0(298 K), at 298 K and ΔlgHm0(Tb), at hypothetical normal boiling point, were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL HPReO4, α, was calculated, and in comparison with experimental value, the magnitude order is in good agreement by 3.32 %.
33 citations
TL;DR: In this article, a roughly linear relationship between So and ΔHo was found for 32 solids and CODATA results for another 45, which supports the thesis that thermodynamic entropy and stored internal energy in a solid are intimately related.
Abstract: As a substance is heated at constant pressure from near 0 K to 298 K, each incremental enthalpy increase, dH, alters entropy by dH/T, bringing it from approximately zero to its standard molar entropy So. Using heat capacity data for 32 solids and CODATA results for another 45, we found a roughly linear relationship between So and ΔHo. The plot showing the relationship So ≈ (constant)ΔHo, with constant = 0.0066 K–1, for 77 solids can serve as an enlightening visualization of this relationship for students in general chemistry. The near-linearity can be understood qualitatively in terms of lattice vibrations and internal vibrations within polyatomic units, which are reflected by molar heat capacities and Debye temperatures. This study supports the thesis that thermodynamic entropy and stored internal energy in a solid are intimately related and that entropy can be usefully interpreted as a spreading function, as described in the text.
TL;DR: The sorption of Ni(II) on montmorillonite was strongly dependent on pH values and temperature, and independent of ionic strength, and at alkaline pH the sorption is dominated by inner-sphere surface complexation.
TL;DR: In this article, the chemical potentials of CaO in two-phase fields were measured in the temperature range (900 to 1250) K, relative to pure CaO as the reference state, using solid state galvanic cells incorporating single crystal CaF2 as the solid electrolyte.
TL;DR: In this article, the Gibbs free energy of kornelite, paracoquimbite, Fe 2 (SO 4 ) 3 ·5H 2 O, and Fe 2(SO 4 ), as a function of temperature and relative humidity of air is calculated.
Abstract: Enthalpies of formation of kornelite [Fe 2 (SO 4 ) 3 ·~7.75H 2 O] and paracoquimbite [Fe 2 (SO 4 ) 3 ·9H 2 O] were measured by acid (5 N HCl) solution calorimetry at T = 298.15 K. The samples were characterized chemically by an electron microprobe, and structurally by the means of single-crystal, in-house powder, and synchrotron powder X-ray diffraction. The refined structures for the two phases are provided, including estimates of the positions and concentration of non-stoichiometric water in structural channels of kornelite, location of the hydrogen atoms and the hydrogen bonding system in this phase. The measured enthalpies of formation from the elements (crystalline Fe, orthorhombic S, ideal gases O 2 and H 2 ) at T = 298.15 K are −4916.2 ± 4.2 kJ/mol for kornelite and −5295.4 ± 4.2 kJ/mol for paracoquimbite. We have used several algorithms to estimate the standard entropy of the two phases. Afterward, we calculated their Gibbs free energy of formation and constructed a phase diagram for kornelite, paracoquimbite, Fe 2 (SO 4 ) 3 ·5H 2 O, and Fe 2 (SO 4 ) 3 as a function of temperature and relative humidity of air. The topology of the phase diagram is very sensitive to the entropy estimates and the construction of a reliable phase diagram must await better constraints on entropy or Gibbs free energy of formation. Possible remedies of these problems are also discussed.
TL;DR: The temperature-dependent solubility of hexanitrostilbene (HNS) was determined in ten solvents and solvent blends using the Tyndall effect as mentioned in this paper.
Abstract: The temperature-dependent solubility of hexanitrostilbene (HNS) [CAS# 20062-22-0] was determined in ten solvents and solvent blends using the Tyndall effect. Thermodynamic modeling of the data yielded Flory interaction parameters, the molar enthalpy of mixing, the molar entropy of mixing, and the molar Gibbs energy of mixing. All solutions exhibited endothermic enthalpies and positive entropies of mixing. The presence of water in some of the solvent blends made dissolution increasingly endothermic and disfavored solubility. The solubilities of HNS at 25 °C were used to determine the three-component Hansen solubility parameters (HSP) (δD=18.6, δP=13.5, δH=6.1 MPa1/2) and the radius of the solubility sphere (R0=5.8 MPa1/2). The HSP determined for HNS using group-additivity (δD=21.0, δP=13.3, and δH=8.6 MPa1/2) also correctly predicted the optimum solvents for this explosive.
TL;DR: In this paper, the authors combine results from pulsed-laser experiments and a thermodynamic analysis, to separate temperature effects on double-layer and charge-transfer processes, and compare the corresponding entropy of formation of the overall interphase.
Abstract: The present work combines results from pulsed-laser experiments and a thermodynamic analysis, to separate temperature effects on double-layer and charge-transfer processes. The entropy of formation of the double layer for Pt(111) in 0.1 M HClO4 is evaluated and compared with the corresponding entropy of formation of the overall interphase. The difference between the two quantities is due to the entropy change associated with charge-transfer processes, thus allowing for the evaluation of the absolute molar entropy of adsorbed hydrogen and OH on Pt(111). The results indicate that adsorbed hydrogen on Pt(111) is very mobile, whereas adsorbed OH species are rather immobile. Finally, values of the entropy of formation of the double layer are compared to data for mercury electrodes. It is concluded that the entropy of the interfacial water network on Pt(111) exhibits a nearly symmetrical dependence on charge density. This result contrasts with the behavior observed for mercury electrodes, for which the state of...
TL;DR: In this paper, the standard molar enthalpies of combustion of 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde were measured by static bomb combustion calorimetry.
TL;DR: In this paper, the heat capacity of two synthetic spessartine samples (Sps) was measured on 20-30-mg-size samples in the temperature range 2-864-K by relaxation calorimetry (RC) and differential scanning (DSC).
TL;DR: In this paper, the authors define a renormalized entropy, which is related with the Newton-Wigner position operator, and show that it is free of divergences and has a perfectly sound thermodynamic behavior in the high temperature/big volume limit.
Abstract: Standard entropy calculations in quantum field theory, when applied to a subsystem of definite volume, exhibit area-dependent UV divergences that make a thermodynamic interpretation troublesome. In this paper we define a renormalized entropy which is related with the Newton-Wigner position operator. Accordingly, whenever we trace over a region of space, we trace away degrees of freedom that are localized according to Newton-Wigner localization but not in the usual sense. We consider a free scalar field in d+1 spacetime dimensions prepared in a thermal state and we show that our entropy is free of divergences and has a perfectly sound thermodynamic behavior. In the high temperature/big volume limit our results agree with the standard QFT calculations once the divergent contributions are subtracted from the latter. In the limit of low temperature/small volume the entropy goes to zero but with a different dependence on the temperature.
TL;DR: In this article, the effect of sulfonation level and domain size of hydrophilic channels on humidity-induced phase transitions in poly(styrenesulfonate−methylbutylene) (PSS−PMB) block copolymers was studied as a function of the relative humidity and temperature of the surrounding air by a combination of water uptake measurements and in situ small-angle neutron scattering.
Abstract: The effect of sulfonation level and domain size of hydrophilic channels on humidity-induced phase transitions in poly(styrenesulfonate−methylbutylene) (PSS−PMB) block copolymers was studied as a function of the relative humidity (RH) and temperature of the surrounding air by a combination of water uptake measurements and in situ small-angle neutron scattering. The equality of the chemical potential of water in the gas and polymer phases was exploited to determine the change in the partial molar entropy of water at order−disorder transitions. PSS−PMB samples with 5 nm domain spacing exhibited a disorder-to-order transition with increasing temperature at fixed RH, while the PSS−PMB samples with 7 nm domain spacing exhibited an order-to-disorder transition with increasing temperature at fixed RH. There is evidence to suggest that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules, while the order-to-disorder transition is driven by more familiar driv...
TL;DR: In this paper, the standard molar enthalpies of 2,5 and 2,6-dichloro-4-nitroanilines in the gaseous phase were derived from the standard massic energies of combustion of the two isomers, in oxygen, at T =298.15 K, measured by rotating-bomb combustion calorimetry.
TL;DR: In this article, a statistical thermodynamic calculation is carried out and calculated results are compared to those obtained from experimental data in order to elucidate the relation between thermodynamic quantities, the defect structure, and the defect equilibrium in La 2− x Sr x NiO 4+ δ.
TL;DR: A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters as mentioned in this paper.
Abstract: A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters. Batch adsorption studies were carried out to evaluate the effect of pH, contact time, initial concentration (28–100 mg/g), adsorbent dose (0.05–0.3 g), and temperature (290–323 K) on the removal of BB3. The adsorption equilibrium data were analyzed by the Langmuir, Temkin, and Freundlich isotherm models, with the best fitting being the first one. The adsorption capacity (Qo) increased with increasing initial dye concentration, adsorbent dose, and temperature; the highest maximum Qo (59.53 mg/g) was obtained at 323 K. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion models were used to analyze the kinetic data; good agreement between the experimental and calculated amounts of dye adsorbed at equilibrium were obtained for the pseudo-second-order kinetic models for the entire investigated concentrations domain. Various thermodynamic parameters, such as standard enthalpy of adsorption (ΔHo = 88.817 kJ/mol), standard entropy of adsorption (ΔSo = 0.307 kJ mol−1 K−1), and Gibbs free energy (ΔGo < 0, for all temperatures investigated), were evaluated and revealed that the adsorption process was endothermic and favorable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
TL;DR: In this paper, a new competitive adsorption isothermal model (CAIM) was developed for the coexistent and competitive binding of heavy metals to the soil surface, which was compared with the Langmuir model using different conditions.
TL;DR: In this article, defect chemical and statistical thermodynamic analyses were carried out to elucidate how oxygen content changes in Nd 2−− x Sr x NiO 4+− δ ( x ǫ = 0, 0.2, 04), defect chemical analysis was carried out and the relationship among δ, P (O 2 ), and T were analyzed by a defect equilibrium model.
TL;DR: The analysis of reported data here presented provides a self-consistent set of entropies for cations and charge-independent values for anions, and an unexpected and significant observation is that cations are related to the molar volumes of the corresponding (neutral) condensed-phase metals.
Abstract: Single-ion standard entropies, S(ion)(o), are additive values for estimation of the room-temperature (298 K) entropies of ionic solids. They may be used for inferring the entropies of ionic solids for which values are unavailable and for checking reported values, thus complementing the independent method of estimation from molar volumes (termed volume-based thermodynamics). Current single-anion entropies depend on the charge of the countercation, and so are difficult to apply to complex materials, such as minerals. The analysis of reported data here presented provides a self-consistent set of entropies for cations and charge-independent values for anions. Although the S(ion)(o) values presented encompass only a limited set of ions, the retrieval of values for ions not listed is straightforward and is described. An unexpected and significant observation is that cation entropies are related to the molar volumes of the corresponding (neutral) condensed-phase metals.
TL;DR: In this paper, the standard molar enthalpy of 4,5-dichloro-2-nitroaniline, in the gaseous phase, at T =298.15 K, was derived from the combination of the values of the standard Molar Enthalpy in the crystalline phase and the standard MCI of sublimation, at the same temperature.
TL;DR: In this paper, the low-temperature heat capacity of NiAl 2 O 4 and CoAl O 4 was measured between T = 4 and 400 K and thermodynamic functions were derived from the results.
01 Jan 2009
TL;DR: In this article, the properties of polymers and their properties in terms of specific and molar heat capacities are discussed. But the properties are only available for a few polymers, and they are not available for all polymers.
Abstract: Publisher Summary
This chapter deals with the calorimetric properties of polymers. The following properties belong to the calorimetric category: specific and molar heat capacities, latent heats of crystallization, or fusion. The specific heat capacity is the heat that must be added per kg of a substance to raise the temperature by one Kelvin or one degree Celsius. The molar heat capacity is the specific heat multiplied by the molar mass. Reliable values for the molar heat capacity in the solid and the liquid state are available for a limited number of polymers only. This emphasizes the importance of correlations between the chemical and the physical structure of polymers. The latent heat of fusion (crystallization) or the enthalpy difference is an important quantity for the calculation of other thermodynamic functions. Furthermore, knowledge of the latent heat of fusion is necessary for the design of a number of polymer processing apparatuses. Reliable experimental values for latent heat of fusion are available, however, for a limited number of polymers only. Based on this understanding, this chapter demonstrates that both groups of properties can be calculated as additive molar quantities. Finally, it suggests that starting from these properties the molar entropy and enthalpy of polymers can be estimated.
TL;DR: In this article, single crystals of ZnBi2B2O7 (ZBBO) have been successfully grown by the top-seeded growth method from a high-temperature melt.