Showing papers on "Standard molar entropy published in 2016"
15 Aug 2016
TL;DR: The equilibrium, kinetics, and thermodynamics of the biosorption of Pb, Cd, and Zn onto groundnut shell were investigated under various physicochemical parameters.
Abstract: The equilibrium, kinetics, and thermodynamics of the biosorption of Pb(II), Cd(II) and Zn(II) onto groundnut (Arachis hypogaea) shell were investigated under various physicochemical parameters. Optimisation studies were carried out using batch biosorption studies. The extent of the metal ion biosorption increased with increase in solution pH, initial metal ion concentration, dosage of biosorbent and contact time but decreased with the temperature of the system. The biosorption of each of the metal ions was found to be pH-dependent. Kinetic study showed that the metal ions biosorption process followed the pseudo-second-order kinetic model. The sorption of each metal ion was analysed with Freundlich and Langmuir isotherm models, in each case, the equilibrium data were better represented by Freundlich isotherm model. Thermodynamically, parameters such as standard Gibbs free energy (∆ G˚), standard enthalpy (∆ H˚), standard entropy (∆ S˚) and the activation energy ( A) were calculated. The biosorption of each metal ion was spontaneous and the order of spontaneity of the biosorption process being Cd(II) > Zn(II) > Pb(II). Similarly, change in entropy was observed for each and the order of disorder is Cd(II) > Zn(II) > Pb(II).
120 citations
TL;DR: In this paper, the authors describe tools, developed over recent years, which make it easy to estimate often elusive thermodynamic parameter values, generally for ionic materials, both solid and liquid, as well as for their solid hydrates and solvates.
Abstract: The application of thermodynamics is simple, even if the theory may appear intimidating We describe tools, developed over recent years, which make it easy to estimate often elusive thermodynamic parameter values, generally (but not exclusively) for ionic materials, both solid and liquid, as well as for their solid hydrates and solvates The tools are termed volume-based thermodynamics (VBT) and thermodynamic difference rules (TDR), supplemented by the simple salt approximation (SSA) and single-ion values for volume, Vm, heat capacity, , entropy, , formation enthalpy, ΔfH°, and Gibbs formation energy, ΔfG° These tools can be applied to provide values of thermodynamic and thermomechanical properties such as standard enthalpy of formation, ΔfH°, standard entropy, , heat capacity, Cp, Gibbs function of formation, ΔfG°, lattice potential energy, UPOT, isothermal expansion coefficient, α, and isothermal compressibility, β, and used to suggest the thermodynamic feasibility of reactions among condensed ionic phases Because many of these methods yield results largely independent of crystal structure, they have been successfully extended to the important and developing class of ionic liquids as well as to new and hypothesised materials Finally, these predictive methods are illustrated by application to K2SnCl6, for which known experimental results are available for comparison A selection of applications of VBT and TDR is presented which have enabled input, usually in the form of thermodynamics, to be brought to bear on a range of topical problems Perhaps the most significant advantage of VBT and TDR methods is their inherent simplicity in that they do not require a high level of computational expertise nor expensive high-performance computation tools – a spreadsheet will usually suffice – yet the techniques are extremely powerful and accessible to non-experts The connection between formula unit volume, Vm, and standard thermodynamic parameters represents a major advance exploited by these techniques
65 citations
TL;DR: In this article, large scale quantum calculations for molar enthalpy of formation (Delta(f) H-0, standard entropy (S-0), and heat capacity (C-V) are presented.
Abstract: Large scale quantum calculations for molar enthalpy of formation (Delta(f) H-0), standard entropy (S-0), and heat capacity (C-V) are presented. A large data set may help to evaluate quantum thermoc ...
58 citations
TL;DR: An experimental Raman study on how the addition of sodium chloride to CO2-hydrate-forming systems inhibits the hydrate formation thermodynamically, using the Raman spectrum of the water-stretching vibration.
Abstract: We present an experimental Raman study on how the addition of sodium chloride to CO2-hydrate-forming systems inhibits the hydrate formation thermodynamically. For this purpose, the molar enthalpy of reaction and the molar entropy of reaction for the reaction of weakly hydrogen-bonded water molecules to strongly hydrogen bonded water molecules are determined for different salinities from the Raman spectrum of the water-stretching vibration. Simultaneously, the influence of the salinity on the solubility of CO2 in the liquid water-rich phase right before the start of hydrate formation is analyzed. The results demonstrate that various mechanisms contribute to the inhibition of gas hydrate formation. For the highest salt concentration of 20 wt % investigated, the temperature of gas hydrate formation is lowered by 12 K. For this concentration the molar enthalpy and entropy of reaction become smaller by 50 and 20%, respectively. Concurrently, the solubility of carbon dioxide is reduced by 70%. These results are...
51 citations
01 Jan 2016
TL;DR: In this paper, the authors define an entropy of rational maps of a smooth projective variety X to itself in terms of the growth rate of the volumes of its subvarieties.
Abstract: In this note we define an entropy of rational maps of a smooth projective variety X to itself in terms of the growth rate of the volumes of its subvarieties. We give a formula for this entropy in terms of the spectral radius of the iterates of the induced maps on the homology subgroups of X generated by analytic cycles. In the case of holomorphic maps we show that this entropy is the standard entropy which is equal to the log of the spectral radius of the induced
50 citations
TL;DR: In this article, the effects of various parameters such as adsorbent dosage, pH, contact time, and temperature on the equilibrium constant were studied and the thermodynamic parameters like standard Gibb's free energy, standard enthalpy, and standard entropy were also investigated.
34 citations
TL;DR: In this paper, the results predict an endothermic nature of adsorption and a spontaneous process, and a pseudo-second order model could best describe the adorption kinetics.
34 citations
TL;DR: The experimental data of aqueous-ethanolic solutions as a function of SDS concentration ranging from 1 to 14mM−dm −3 show the presence of inflexion points indicating micellization and interaction mechanisms as mentioned in this paper.
32 citations
TL;DR: In this article, the authors used density functional perturbation theory to reveal the interplay between thermodynamics and mechanical properties in the transformation of studtite into metastudtite.
Abstract: The interplay between thermodynamics and mechanical properties in the transformation of studtite, (UO2)(O2)(H2O)2·2H2O, into metastudtite, (UO2)(O2)(H2O)2, two important corrosion phases observed on the surface of uranium dioxide exposed to water, is revealed using density functional perturbation theory. Phonon calculations within the quasi-harmonic approximation predict that the standard entropy change for the (UO2)(O2)(H2O)2·2H2O → (UO2)(O2)(H2O)2 + 2H2O reaction is ΔS0 = +80 J·mol–1·K–1 for the production of water in the liquid state and +389 J·mol–1·K–1 for water vapor. Similar to bulk H2O(l), the bulk modulus of (UO2)(O2)(H2O)2·2H2O increases with temperature, contrasting with (UO2)(O2)(H2O)2 which features the typical Anderson–Gruneisen temperature dependence of oxide solids. Upon removal of interstitial H2O in studtite, the most important changes in the shear modulus, the parameter limiting the mechanical stability, arise in the planes normal to chain propagation directions. The present findings ha...
32 citations
TL;DR: In this article, five DMEA-based protic ionic liquids (PILs) with carboxylates were synthesized and physicochemical properties such as density (ρ) and speed of sound (u) were measured as a function of temperature from (293.15-343.15) K at 0.1
25 citations
TL;DR: In this paper, the solubility data of one polymorph of Ala-Gln (form II) in binary methanol+water and isopropanol+water solvents mixtures from 278.15 to 313.15 K were determined by using a dynamic method under atmospheric pressure.
TL;DR: In this paper, the Zr(V1−xNix)2 intermetallic compounds were prepared by the arc-melt method and annealed 1273 K for 168h.
TL;DR: In this paper, two pyrrolidonium-based ionic liquids were synthesized and characterized by 1 H NMR spectroscopy technique, and the experimental density, speed of sound, viscosity and conductivity have been measured in the temperature range of (293.15-333.15) K and at 0.1-MPa pressure.
TL;DR: In this paper, the low-temperature molar heat capacities of Rhodamine B (225-320 K) and Rhodamine 6G (225 −440 K) were determined on a modulated differential scanning calorimetry (MDSC).
Abstract: Heat capacity is a very important thermodynamic parameter of any compound. How to precisely measure the heat capacity is a long-sought task. In this study, the low-temperature molar heat capacities of Rhodamine B (225–320 K) and Rhodamine 6G (225–440 K) were determined on a modulated differential scanning calorimetry (MDSC). There is no thermal anomaly or phase transition observed for Rhodamine B from 225 to 320 K. However, a phase transition appears for Rhodamine 6G with a peak temperature of 373 K, and the onset temperature is at 349.4 ± 0.4 K. The molar enthalpy ΔH
trans and molar entropy ΔS
trans for this phase transition are determined to be 2.310 ± 0.011 kJ mol−1 and 6.611 ± 0.032 J K−1 mol−1, respectively. According to the measured molar heat capacities, the entropy and enthalpy referenced to the temperature of 298.15 K for Rhodamine B and Rhodamine 6G are derived. Moreover, thermogravimetric analysis (TG) is employed to investigate their thermal stability. The initial decomposition temperature for Rhodamine B and Rhodamine 6G is 326.5 and 492.1 K, respectively. There are two steps of mass loss observed for Rhodamine 6G and three steps for Rhodamine B.
TL;DR: In this article, the effect of co-solvent N-methylacetamide (NMA) and cationic surfactant cetyltrimethylammonium bromide (CTAB) on micellization was explored by employing conductivity measurements at different temperatures (298.15-313.15 K).
Abstract: The effect of co-solvent N-methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg−1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg−1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg−1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔH
m
o
, standard entropy change, ΔS
m
o
, and standard Gibbs free energy change, ΔG
m
o
, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants.
TL;DR: In this article, the heat capacity of brookite TiO2 was measured using a Quantum Design physical property measurement system (PPMS) in the temperature range of 2.K to 300 K.
TL;DR: In this article, the adsorption of acid blue 129 (AB129) from aqueous solution onto montmorillonite clay (HCl-bentonite) was investigated.
Abstract: The adsorption of Acid Blue 129 (AB129) from aqueous solution onto hydrochloric acid-activated montmorillonite clay (HCl-bentonite) was investigated. The activated clay was characterized by scanning electron microscopy, energy dispersive spectroscopy, and Brunauer–Emmett–Teller surface area. Batch adsorption experiments were performed to investigate the effects of pH, contact time, initial dye concentration, and temperature (10, 20, 30, and 40°C). Acidic conditions was suitable for higher adsorption of AB129, and kinetic studies demonstrate that the process followed a pseudo-second-order model. An activation energy of 23.858 kJ mol−1 was obtained for adsorption process. Adsorption data were fitted to Freundlich and Langmuir isotherms and various adsorption parameters have been calculated. Standard enthalpy (ΔH°) and standard entropy (ΔS°) were −44.90 kJ mol−1 and −68.44 kJ mol−1 K−1, respectively, showing that overall adsorption process was exothermic and is spontaneous in nature with a decrease i...
TL;DR: This paper reviews the recent methodological advances of the use of ACE in studying the complex equilibria of radionuclides in aqueous solutions and special attention is paid to a number of species involved in equilibrium.
Abstract: Interaction of radionuclides with inorganic and organic species present in natural environment plays an important role in their eventual dispersion. The complex equilibria established in the aqueous phase cause significant changes in the migration properties of radionuclides. Affinity capillary electrophoresis (ACE) can be fruitful in studying these equilibria. This paper reviews the recent methodological advances of the use of ACE in studying the complex equilibria of radionuclides in aqueous solutions. Special attention is paid to the determination of a number of species involved in equilibrium, species constituents (number of ligands, protonated, deprotonated), the influence of ionic strength and temperature on stability constants of complex species formed. Use of ACE for the determination of the main thermodynamic parameters (the molar Gibbs energy (Δr Gm ), the molar enthalpy (Δr Hm ) and the molar entropy (Δr Sm )) of complex formation reactions is also discussed. These data are essential to predict dispersion of radionuclides in the natural environment.
TL;DR: In this article, stable and metastable crystal phases of 1-butyl-3-methylimidazolium hexafluorophosphate were obtained in an adiabatic calorimeter providing precise temperature control during crystallization.
TL;DR: In this paper, the heat capacity measurements of the crystalline phosphate CsCoPO4 with a β-tridymite structure were performed between T = 6 and 650 K, where the phase transitions correspond to the polymorphic transformations between two monoclinic and two orthorhombic modifications.
TL;DR: In this article, the removal of UDMH as a pollutant with considerable toxicity is studied using activated carbon magnetic nanocomposite with fast and easy separation, and effective parameters, such as pH, adsorbent dosage, contact time, and temperature, have been investigated.
Abstract: In this work, removal of UDMH as a pollutant with considerable toxicity is studied using activated carbon magnetic nanocomposite with fast and easy separation. To optimize the process, effective parameters, such as pH, adsorbent dosage, contact time, and temperature, have been investigated. More than 90% UDMH removal efficiency obtained within 30 min of contact time, 20 mg of adsorbent at pH 6 and room temperature. The adsorption behavior was evaluated based on equilibrium data, using both the Langmuir and Freundlich isotherm models. It was found that adsorption data were interpreted by Freundlich model better than Langmuir model with regression coefficient of 0.9971. Besides, the adsorption data were well described by the pseudo-second-order kinetic model. The adsorption thermodynamic parameters showed that the adsorption process is endothermic and spontaneous with positive standard enthalpy of 2.74 J mol−1 and negative standard free energy of 29.08 kJ mol−1, respectively. Also standard entropy c...
TL;DR: In this paper, five protic ionic liquids (PILs) have been synthesized through atom economic neutralization reaction between N-butyl hydroxyethyl amine and bronsted acid RCOOH, where R is H, CH 3, C 2 H 5, C 3 H 7, and C 4 H 9.
TL;DR: In this article, LiCoO2 was prepared by solid state route and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), magnetic properties measurement and simultaneous thermal analysis (STA).
TL;DR: In this article, the spin state and exchange integral of cobalt ions in stoichiometric ZnCo2O4 nanoparticles with varying particle size from about 24 to 105 nm were reported.
Abstract: This work reports on spin state and exchange integral of cobalt ions in stoichiometric ZnCo2O4 nanoparticles with varying particle size from about 24 to 105 nm. Cobalt ions in ZnCo2O4 nanoparticles are present as trivalence in mixed spin state. The effective magnetic moment is distributed in the range of 2.1 ∼ 1.31 μB at room temperature with coarsening of nanoparticles. Further, it is demonstrated that stoichiometric ZnCo2O4 undergoes a magnetic transition from paramagnetism to antiferromagnetism with decrease of temperature, showing a transition temperature of about 5 K. The standard molar entropy and enthalpy for 24 nm ZnCo2O4 are 170.6 ± 1.7 J K−1 mol−1 and 28.2 ± 0.3 kJ mol−1 at 298.15 K, respectively. Based on the heat capacity data, the exchange integral is determined to be 4.16 × 10−22 J. The results report here are really important for further understanding the magnetic and electronic properties of spinel oxides.
TL;DR: In this paper, the influence of ascorbic acid and temperature on the micellization of a cationic gemini surfactant, hexanediyl-1,6-bis (dimethylcetylammonium bromide), 16-6-16 was investigated.
Abstract: Herein, we report the study of the influence of ascorbic acid and temperature on the micellization of a cationic gemini surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide), 16-6-16. The critical micelle concentration (CMC) of 16-6-16 was measured by the conductivity method and dye solubilisation technique. A tendency of the CMC values to increase with temperature and upon the adding of ascorbic acid was found. The standard Gibbs energy, standard enthalpy, and standard entropy of micellization of 16-6-16 were evaluated. The results of calculations suggest the decrease of the stability of the 16-6-16 micellar solution in the presence of ascorbic acid.
TL;DR: In this article, the effects of variation of temperature, composition of the binary solvents mixtures and the type of the solvent in the solubility were discussed, and the temperature dependence of the experimental data in binary mixtures was well correlated by the modified Apelblat model.
TL;DR: In this paper, the interaction between polyvinylpyrrolidone (PVP) and gemini surfactant (16- 5 -16) in aqueous solution has been analyzed using conductometry.
Journal Article•
TL;DR: In this article, the molecular structure of high energy compound 1-phenyl-2-nitroguanidine at B3LYP/6-311++G(d,p) level was analyzed using Gaussian 03 software package.
Abstract: The DFT study was carried out using Gaussian 03 software package to appraise the molecular structure of high energy compound 1-phenyl-2-nitroguanidine at B3LYP/6-311++G(d,p) level. Natural Bond Orbital (NBO) analysis of the molecule was carried out in order to understand the electronic structure and hybridization of the atoms at same level of theory. The hyper conjugative interactions and charge delocalization acquired from NBO analysis was used to investigate the stability of compound. The π electron delocalization parameter (Q) as a geometrical indicator of a local aromaticity and the geometry based Harmonic Oscillator Measure Aromaticity (HOMA) have also been calculated at the same level of theory. The electron density based Fukui function was used to envisage the reactive site. On the basis of the principle of statistical thermodynamics, the standard molar heat capacity (oÂÂ¥o®,o« θ ), standard molar entropy (oµo« θ ) and standard molar enthalpy (oÂÂao« θ ) from 200 to 800 K were derived from the scaled frequencies. The dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule have also been reported.
TL;DR: In this paper, the temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph3Sb(OC(O)Ph)2 was studied in the range of 6-480 K by means of precision adiabatic vacuum calorimetry and differential scanning calors.
Abstract: The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph3Sb(OC(O)Ph)2 is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph3Sb(OC(O)Ph)2 is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph3Sb(OC(O)Ph)2 in the crystalline and liquid states are calculated from the obtained experimental data: C
°
(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.
TL;DR: In this paper, the temperature dependences of heat capacity of triphenylantimony dicrotonate Ph3Sb(O2CCH=CHCH3)2 and Triphenylbismuth dibismuth Ph3Bi(O 2CCH = CHCH 3)2 were studied by means of precision adiabatic vacuum calorimetry and differential scanning caloreimetry over the temperature range from 6.5 to 490 K.
Abstract: In the present research, the temperature dependences of heat capacity of triphenylantimony dicrotonate Ph3Sb(O2CCH=CHCH3)2 and triphenylbismuth dicrotonate Ph3Bi(O2CCH=CHCH3)2 were studied by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry over the temperature range from 6.5 to 490 K. The thermal stability of the samples was investigated by thermogravimetric analysis. The experimental data were used to calculate the standard thermodynamic functions: heat capacity, enthalpy, entropy, and Gibbs energy over the range from T → 0 to 400–420 K. For the compounds under study, the standard entropy of formation was calculated at T = 298.15 K.