Entropy Of Formation Research Articles

Thermodynamic properties of microorganisms: determination and analysis of enthalpy, entropy, and Gibbs free energy of biomass, cells and colonies of 32 microorganism species

Thermodynamic analysis is an important part of chemical engineering. However, its application in biotechnology has been hampered by lack of data on thermodynamic properties of microorganism biomass. In this paper, a review was made of methods for estimation of thermodynamic properties of biomass, including standard enthalpy of combustion hC⁰, enthalpy of formation hf⁰, entropy s⁰, and Gibbs free energy of formation gf⁰. These parameters were calculated on molar and mass specific basis for 32 microorganism species, including 14 bacteria, 7 yeast and 11 algae species. It was found that hf⁰, s⁰, gf⁰ are, respectively, similar for all the analyzed species, due to the fact that all living organisms have a common ancestor and thus a similar chemical composition. Furthermore, all the analyzed microorganisms have negative hf⁰, originating from partial oxidation of all other elements by oxygen and nitrogen. A brief review was given of microorganism endogenous and growth metabolic rates. Finally, based on the determined thermodynamic properties, entropy of individual E. coli and Pseudomonas cells were determined and entropy of a Pseudomonas colony during its lifespan was calculated and analyzed. Three periods can be distinguished in the existence of a microorganism colony: (a) accumulation period when cell number, mass and entropy increase, (b) steady state period when they are approximately constant, and (c) decumulation period when they decrease.

Thermodynamic properties of praseodymium on the liquid cadmium electrode and evaluation of anodic dissolution behavior in LiCl-KCl eutectic

The electrochemical and thermodynamic properties of Pr on a liquid Cd electrode and the formation of Cd-Pr intermetallic compounds were systematically studied by a series of electrochemical techniques in LiCl-KCl eutectic. The activity coefficient of Pr in the liquid Cd was determined by galvanostatic intermittent titration and in-situ open circuit chronopotentiometry at various temperatures. The measurement of electromotive force was conducted to calculate the partial molar Gibbs free energies of Pr in two phase coexisting states. In addition, the thermodynamic parameters of seven Cd-Pr intermetallic compounds such as the Gibbs free energy, enthalpy and entropy of formation were also determined. The deposited Cd-Pr alloy sample was prepared by galvanostatic electrolysis and further characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). The dissolution behavior of Cd-Pr alloy as an anode material was also evaluated by monitoring the variation of anodic potential.

Redetermination of low-temperature heat capacity of Cu(C5H7O2)2

The heat capacity of copper bis-acetylacetonate (Cu(C5H7O2)2) was measured over the temperature range (6.54–313.16) K by adiabatic-shield calorimetry. No anomalies associated with phase transition were found in the functional heat capacity behaviour. The Debye temperature at 0 K was calculated. The data obtained were used to calculate its thermodynamic functions (entropy, enthalpy, reduced Gibbs energy) in the range (0–313) K. They have the following values at 298.15 K: Cp° = (283.9 ± 0.5) J K−1 mol−1, Δ0298.15Sm° = (359.1 ± 0.8) J K−1 mol−1, Δ0298.15Hm° = (50.94 ± 0.09) kJ mol−1, Φm° = (188.3 ± 1.1) J K−1 mol−1. The value of the absolute entropy were used to calculate the entropy of formation of Cu(C5H7O2)2 (cr) at T = 298.15 K. The universal heat capacity behaviour of metal acetylacetonates was demonstrated in a wide temperature range.

Biogas Plasticization Coupled Anaerobic Digestion: Anaerobic Pump Calorimetry.

This paper presents the quantitative bomb calorimetric high heat values (HHV) for residue samples collected from the Anaerobic Pump (®TAP) and a continuous flow stirred tank reactor (CFSTR) anaerobically digesting a 50:50 wastewater sludge substrate. TAP, an advanced anaerobic digestion (AD) process, features biogas plasticization that greatly increases gas production and leaves a mineralized residual. Measured residue HHVs are compared to HHV estimates from literature empirical relationships. Two empirical formulations, the Meraz thermodynamic formulation (with 7.4% moisture) (Meraz et al. The Chemical Educator, 7(2), 66-70, (2002) and the Channiwala Universal formulation (Channiwala et al. Fuel, 81(8), 1051-1063, (2002), compared favorably (within ± 3% mean value) with the bomb measured HHV values. A stoichiometric ICC description for Ucells is derived. The thermodynamic formation potentials of all measured residues are derived including Ucells. An empirical method was used to calculate the entropy of formation (∆fS) for all residues and Ucells. Krevelen plots show residue molar ratios of oxygen and hydrogen to carbon (H/C, O/C) are linearly correlated with HHV and formation potentials (∆fG', ∆fH', ∆fS') with strong statistical coefficients of determination (R2). Residue H/C and O/C ratios fell across the peat classification on the biomass coalification diagram. A wide AD methane fermentation zone ≤ 18.6 MJ/kg is identified. The methods and correlation relationships presented enable the computation of accurate HHV and thermodynamic formation potentials without the necessity of direct thermal measurement. These quantitative results confirm that steady state AD of a well-known heterogeneous solid substrate (WWTP sludge) is a linear thermodynamic process.

Thermodynamic Study of Siver—Tin Selenides by the EMF Method with Ag4RbI5 Solid Electrolyte

The system Ag-Sn-Se in the region of Ag2Se-SnSe-Se composition is studied by measuring EMF of cells with Ag4RbI5 solid electrolyte in the temperature interval of 300–450 K. Based on the results of EMF measurements, the temperature of Ag8SnSe6 polymorphous transition (355 K) is determined and the partial molar functions of silver in certain phase regions of this system are calculated. Standard thermodynamic functions of formation and standard entropies are estimated for ternary phases AgSnSe2, Ag0.84Sn1.16Se2, and two modifications of Ag8SnSe6 and also thermodynamic functions of Ag8SnSe6 polymorphous transition.

(Invited) Synthesis and Properties of All SWCNT Metallic Nanotube Wire

Copper and aluminum wire conductors are the principal means of conducting electricity. However, they add weight, possess poor fatigue and corrosion resistance and suffer from electromigration under severe conditions. Carbon nanotube (CNT) conductors have long been thought able to replace metals but still fall short of copper in electrical conductivity. CNT wires have so far displaced metal conductors in only a few high value-added applications. In this presentation, we outline an approach to create CNT conductors that address copper shortcomings. These carbon-based wires are made by a new high rate process to grow all metallic (armchair) CNT single wall tubes which are spun into wire in situ within the reactor all in one step, thereby keeping air away from the contacting surfaces of the tubes. We discuss a model of growth in terms of entropy of formation and radiation induced sympathetic vibration. In all other CNT yarn formation methods known to us, multistep processes are required which add cost or omit spinning. This latter process is necessary to add strength and improve conductivity. The innovations described in this talk include (1) methods for synthesis of nearly all metallic single chirality carbon nanotubes, and (2) the in situ spinning of these nanotubes within the reactor to a finished wire. We describe their properties determined by Raman, TGA, and structure by SEM and TEM. The conductivity of CNT wires depends on CNT alignment, surface contamination, control over the interfaces (Schottky barriers), and density. Yarns made from nanotubes of exactly the same diameters are also expected to pack well in the wire and provide better properties than the more typical random and larger diameters sometimes made. The combination of Boronite’s approach to create all CNT wire from uniform nanotubes with metallic chirality with the increasing commercial pressure to reduce weight, increase strength, and operational temperature, opens up commercial opportunities for very lightweight wiring in applications from aircraft to rotating machinery used at high temperatures. Weight saving in a variety of products is especially important for aircraft, cars, and even for large electric systems required to deliver very high current pulses. Boronite has also developed a unique method for infiltrating CNT spun yarn with copper, silver or aluminum to create electromigration resistant materials that can carry extreme currents.

Mathematical assessment of the thermal band gap variation of semiconductors

The thermal band gap variation of ZnS, GaAs, GaP, and ZnSe is mathematically discussed by means of curve discussion. We investigated the most used expressions, i.e. the formulas of Varshni (1967 Physica 34 148) and Fan (1951 Phys. Rev. 82 900). The first and specifically the second derivative of both expressions reveal that Fan’s theory describes the physics behind the thermal affairs, while Varshni’s formula does not. In fact, the second derivative of Fan’s expression pinpoints the temperature at which the maximum of the formation entropy of electron hole pairs takes place, representing the semiconductor’s refractoriness. The work shows that curve discussion verifies whether a mathematical expression describes indeed the physics behind the phenomenon investigated or rather represents simply fitting efficiency.

Investigation of the interfacial properties of platinum stepped surfaces using peroxodisulfate reduction as a local probe

Peroxodisulfate (PDS) reduction has been investigated by electrochemical and FTIR techniques in a wide pH range, on platinum stepped single crystals electrodes vicinal to the (111) pole. PDS reduction is a structure-sensitive reaction and proceeds on well differentiated potential regions for terrace and step sites. This fact allows gaining local information about the individual behavior of those sites. The reaction proceeds at appreciable rate in a narrow potential range, being inhibited in the low and high potential regions of the voltammogram. The inhibition of the reaction at low potentials is most likely associated with a change in the sign of the charge on the electrode, from positive to negative. Therefore, PDS reduction gives an approximate indication of the position of the potential of zero free charge (pzfc). In this way, two local values of pzfc, associated with terrace and steps sites, can be determined. Such values of local pzfc are compared with the local values of potential of maximum entropy (pme) of double layer formation deduced from laser induced T-jump experiment. Good agreement between both magnitudes is found, especially for terraces. The local pzfc on terraces shifts to more positive potentials as the terrace length diminishes, while the local pzfc for steps remains constant. The inhibition of PDS reduction at high potentials can also be related with a second inversion in the sign of the electrode charge. Therefore, PDS reduction can be used to determine a second pzfc on the (111) terraces at high potentials, revealing a non-monotonic charge – potential relationship. Spectroscopic experiments allow the identification of the species involved in PDS reduction.

Spatial structure, thermodynamics and kinetics of formation of hydrazones derived from pyridoxal 5′-phosphate and 2-furoic, thiophene-2-carboxylic hydrazides in solution

The spatial structure of pyridoxal 5′-phosphate hydrazones of 2-furoic hydrazide; thiophene-2-carboxylic hydrazide in aqueous solution was studied by means of quantum chemical calculations and NOE experiment. The hydrazones could exist as a mixture of different conformers; however, the specific ones could be suggested from experimental and calculated data. The stability constants of hydrazones at pH of 1.9; 6.6; 7.0; 7.4 were determined using UV–Vis spectroscopy. Rate constants of the hydrazone formation and hydrolysis reaction within the range of 6.6–7.4 pH were obtained. Isothermal calorimetric titration was performed in order to determine the change in the free Gibbs energy, enthalpy and entropy of hydrazones formation at pH of 6.6. Hydrazones were synthesized and characterized by means of 1H, 13C, 31P NMR, IR, UV–Vis, fluorescent, MS-spectroscopy as well as DSC and elemental analysis.

Thermodynamic Investigation of Polyhydroxylated Derivatives of Light Fullerenes

Isobaric heat capacities of C[Formula: see text](OH)[Formula: see text] and C[Formula: see text](OH)[Formula: see text] fullerenols were measured using adiabatic calorimetry in the temperature range of 0–320[Formula: see text]K along with standard thermodynamic functions: [Formula: see text], [[Formula: see text]] and [[Formula: see text]]. Furthermore, the molar entropy of formation and the molar third law entropy of C[Formula: see text](OH)[Formula: see text] and C[Formula: see text](OH)[Formula: see text] in crystalline state at 298.15[Formula: see text]K were calculated.

Thermodynamics of the DNA Repair Process by Endonuclease VIII

In the present work, a thermodynamic analysis of the interaction between endonuclease VIII (Endo VIII) and model DNA substrates containing damaged nucleotides, such as 5,6-dihydrouridine and 2-hydroxymethyl-3-hydroxytetrahydrofuran (F-site), was performed. The changes in the fluorescence intensity of the 1,3-diaza-2-oxophenoxazine (tC°) residue located in the complementary chain opposite to the specific site were recorded in the course of the enzyme-substrate interaction. The kinetics was analyzed by the stopped-flow method at different temperatures. The changes of standard Gibbs free energy, enthalpy, and entropy of sequential steps of DNA substrate binding, as well as activation enthalpy and entropy for the transition complex formation of the catalytic stage, were calculated. The comparison of the kinetic and thermodynamic data characterizing the conformational transitions of enzyme and DNA in the course of their interaction made it possible to specify the nature of the molecular processes occurring at the stages of substrate binding, recognition of the damaged base, and its removal from DNA.

Evolutionary models of cold and low-mass planets: cooling curves, magnitudes, and detectability

Context.Future instruments like the Near Infrared Camera (NIRCam) and the Mid Infrared Instrument (MIRI) on theJames WebbSpace Telescope (JWST) or the Mid-Infrared E-ELT Imager and Spectrograph (METIS) at the European Extremely Large Telescope (E-ELT) will be able to image exoplanets that are too faint (because they have a low mass, and hence a small size or low effective temperature) for current direct imaging instruments. On the theoretical side, core accretion formation models predict a significant population of low-mass and/or cool planets at orbital distances of ~10–100 au.Aims.Evolutionary models predicting the planetary intrinsic luminosity as a function of time have traditionally concentrated on gas-dominated giant planets. We extend these cooling curves to Saturnian and Neptunian planets.Methods.We simulated the cooling of isolated core-dominated and gas giant planets with masses of 5M⊕–2M♃. The planets consist of a core made of iron, silicates, and ices surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity includes the contribution from the cooling and contraction of the core and of the H/He envelope, as well as radiogenic decay. For the atmosphere we used grey,AMES-Cond,petitCODE, andHELIOSmodels. We considered solar and non-solar metallicities as well as cloud-free and cloudy atmospheres. The most important initial conditions, namely the core-to-envelope-mass ratio and the initial (i.e. post formation) luminosity are taken from planet formation simulations based on the core accretion paradigm.Results.We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5M⊕planet with a 1% H/He envelope with other evolutionary models. We then present the temporal evolution of planets with masses between 5M⊕and 2M♃in terms of their luminosity, effective temperature, radius, and entropy. We discuss the impact of different post formation entropies. For the different atmosphere types and initial conditions, magnitudes in various filter bands between 0.9 and 30 micrometer wavelength are provided.Conclusions.Using blackbody fluxes and non-grey spectra, we estimate the detectability of such planets with JWST. We found that a 20 (100)M⊕planet can be detected with JWST in the background limit up to an age of about 10 (100) Myr with NIRCam and MIRI, respectively.

Synthesis, crystallographic structure and thermodynamic properties of T2-Al2MgC2

T2-Al2MgC2 was synthesized from the elements in a Mg-Al melt at 1000 °C using sealed Ta crucibles. Single crystals of T2-Al2MgC2 were extracted by evaporating the Mg-Al matrix. The crystal structure of T2-Al2MgC2 was refined for the first time on the basis of single-crystal X-ray diffraction. The crystal is trigonal (space group P-3m1, Z = 1) with lattice parameters of a = 3.3767(11) Å, c = 5.807(2) Å and V = 57.34(5) Å3. Based on the refined crystal structure, DFT calculations were conducted to evaluate the thermodynamic properties and the electronic structure of the phase. The heat of formation of T2-Al2MgC2 was calculated to be −23.6 kJ/mol of atoms at 298 K. The heat capacity of T2-Al2MgC2 was measured by DSC from 300 to 871 K and calculated by DFT from 0 to 1000 K. Based on the calculated heat capacity, the entropy of formation of the phase at 298 K was determined to be 70.0 J/mol/K. The band structure and the electronic density of state of T2-Al2MgC2 was calculated leading to an indirect band gap value of 1.73 eV.

Electrochemical Synthesis and Thermodynamic Properties of Pr‐Ni Intermetallic Compounds in a LiCl‐KCl‐NiCl2‐PrCl3 Melt

AbstractIn this report, the electrochemical behaviors of Pr(III) and Ni(II) ions on a W electrode were investigated in LiCl‐KCl eutectic by cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and open‐circuit chronopotentiometry (OCP) techniques. From the results of electrochemical methods, different signals corresponding to seven kinds of intermetallic compounds in the phase diagram of Pr−Ni were observed. The thermodynamic properties of intermetallic compounds in the temperature range of 823–923 K were investigated by open‐circuit chronopotentiometry. With the evaluated apparent standard potentials of Pr−Ni intermetallic compounds, the Gibbs energies, enthalpies and entropies of formation were also calculated. The co‐reduction products by galvanostatic and potentiostatic electrolysis were characterized based on X‐ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDS). The shape of the alloy obviously changes from granular to bulk, and the alloy phase changes from Pr‐rich to Ni‐rich. The co‐reduction products of PrNi5, PrNi2 and PrNi were identified.

Scientific and Practical Bases of a Method of Reception of Thin-Layer Heat-Insulating Coverings

The paper presents a brief overview of the thin-layer thermal insulation paints used now and their characteristics. A new composition of thin-layer heat-insulation coating is proposed. The introduction of solid phases of non-autoclaved foam concrete with the average density D150 with high values of the standard entropy of formation in it is scientifically substantiated from the point of view of increasing the thermal protection properties. It is shown that such phases have an advantage in comparison with the solid phases of the glass and ceramic microspheres used now. It is also proved that the presence of thin-layer thermal insulation coating of nanoscale particles in the form of silica in the composition favours the reflection of the incident heat flux due to the Tindal effect and provides an increase in the polydispersity of the composition. The calculation of the resulting composition by the Van Vleсk formula used in the classical science is given.

A Modified Neumann–Kopp Treatment of the Heat Capacity of Stoichiometric Phases for Use in Computational Thermodynamics

Since the early days of phase diagram calculation, the CALPHAD community has accepted a method of data assessment that is based on using Gibbs energy expressions for stoichiometric compounds that consist of a part that represents the contributions of the reference components, the so-called Neumann–Kopp sum, and a part that represents the Gibbs energy of formation. Usually, the latter consists only of a simple A + B * T term, which implies on the one hand that enthalpy and entropy of formation of a compound are temperature independent, and on the other, that the heat capacity of the respective compound is given by the Neumann–Kopp sum of the Cps of the constituents. In most cases this method yields acceptable results, also for the heat capacity. However, if certain elementary components are involved, this is not so. The paper highlights the problem outlining a remedial treatment that can be applied to problematic heat capacity functions present in pre-existing assessments, and thus giving a suggestion of how to prevent the problem in the future.

Influence of Bi on the temperature dependent fundamental band gap parameters of GaSb1−xBix

The temperature dependent near band edge emission of LPE grown GaSbBi is studied using photoluminescence technique. A two oscillator model is used to obtain the relevant parameters that explain the temperature dependence of band gap more adequately in cryogenic region as compared to the information obtained through the conventional ‘Varshni’ model. The two oscillator model also provides some valuable information on the phonon dispersion co-efficient in GaSb and GaSbBi and its behavior vis-à-vis the bismuth content in the material. Calculations show that the relative contribution of the high energy LA phonon branch increases with increase in Bi concentration and dominate the temperature dependence of band gap. By considering the energy gap as Gibbs free energy of electron and hole pair formation, approximate analytical expressions are derived for the entropy and the enthalpy of the formation process. The entropy of formation of electron-hole pairs is found to decrease with Bi content in GaSbBi indicating an increase in ordering and a decrease of electron- phonon interaction which might explain the reduced temperature dependence of band gap of some III-V-bismides.

Stability of the pyrochlore Tm2Ru2O7(s) & comparison of its stability with other heavy rare earth ruthenium pyrochlores

The Gibbs energy of formation of Tm2Ru2O7(s) has been determined employing a solid-state electrochemical cell incorporating an oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following cell was measured:Cell : (−)Pt/{Tm2O3(s) + Tm2Ru2O7(s) + Ru(s)}//CSZ//O2(p(O2) = 21.21kPa)/Pt(+)The standard molar Gibbs energy of formation of Tm2Ru2O7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by:{ΔfG°(Tm2Ru2O7,s)/(kJ · mol−1) ± 1.9} = − 2511.9 + 0.625 ⋅ (T/K); (977 ≤ T/K ≤ 1265).Standard molar heat capacity Cop,m(T) of Tm2Ru2O7(s), was measured using a heat flux type differential scanning calorimeter (DSC) in two different temperature ranges, from 128 K to 276 K and 307 K to 686 K. The heat capacity in the higher temperature range was fitted into a mathematical expression and can be represented by:C°p,mTm2Ru2O7sT)(J⋅K−1·mol−1=297.8+2.0⋅10−3TK−62.1⋅105/T2K.307≤TK≤686The standard molar heat capacity data of Tm2Ru2O7(s), along with the data obtained from the oxide electrochemical cell were used to calculate the standard enthalpy of formation and absolute molar entropy of the compound. The standard Gibbs energy of formation obtained earlier for other heavy rare earth ruthenium pyrochlores were compared with the present results.

Experimental Framework for Evaluation of the Thermodynamic and Kinetic Parameters of Metal-Oxides for Solar Thermochemical Fuel Production

The two-step metal oxide redox cycle is a promising and thermodynamically attractive means of solar fuel production. In this work, we describe the development of a high-temperature tubular reactor in which the fundamental thermodynamic and kinetic behavior of thermochemical materials can be readily assessed. This reactor system is capable of operating at temperatures up to 1873 K, total pressures ranging from vacuum to ambient, and oxygen partial pressures (pO2) as low as 10−29 atm. Compared to off-the-shelf systems like thermogravimetric analyzers or indirect conductivity-based measurement systems, this system has three inherent benefits: (1) the flexibility to control the sample morphology (e.g., powder, packed bed, reticulated porous ceramic, or pellet), (2) the potential for a well-developed and characterized flow, and (3) the ability to readily customize the system on demand (e.g., easy integration with a steam generator to control and operate at very low pO2). The reactor system and experimental methods were validated by performing isothermal relaxation experiments with undoped ceria, wherein the sample environment was rapidly altered by stepwise changes in the delivered H2O vapor concentration, and comparing measured oxygen nonstoichiometries with accepted data available in the literature. Data were measured at temperatures from 1173 to 1473 K and pO2 from 4.54 × 10−18 to 1.02 × 10−9 atm. The measured equilibrium data displayed strong agreement with the literature and the expected trends were preserved. Kinetic data were extracted by first transforming reactant concentrations measured downstream of the reaction zone using a tanks-in-series mixing model to account for gas dispersion. Next, a mechanistic kinetic model distinguishing surface and bulk species concentrations was fit to the data to extract pertinent thermodynamic and kinetic parameters. The model assumed a two-step reaction mechanism mediated by the formation of an intermediate hydroxyl species on the surface. Activation energies and defect formation enthalpies and entropies for the forward and reverse reactions were found to be in good agreement with previous modeling efforts, providing further validation of the use of this system to explore thermodynamic and kinetic behavior of emerging thermochemical materials.

Benchmark properties of pyrazole derivatives as a potential liquid organic hydrogen carrier: Evaluation of thermochemical data with complementary experimental and computational methods

Abstract The standard molar enthalpy of vaporisation of diphenyl oxide was derived from the vapour pressure temperature dependences measured by the transpiration method. Thermodynamic data on vaporisation processes available in the literature were collected. They were evaluated and combined with our own experimental results. Additional combustion experiment on the highly pure diphenyl oxide helped to resolve ambiguity in the enthalpy of formation for this compound. We have evaluated and recommended the set of vaporisation and formation enthalpies for the diphenyl oxide at 298.15 K (in kJ·mol−1): Δ l g H m o = (66.7 ± 0.2), Δ f H m o (liq) = −(15.8 ± 1.4), and Δ f H m o (g) = (50.9 ± 1.4), as the reliable benchmark properties for further thermochemical calculations. Gas phase molar enthalpy of formation of diphenyl oxide calculated by the high-level quantum-chemical method G4 was in an excellent agreement with the recommended experimental data. The standard molar Gibbs function of formation and the standard molar entropy of formation of diphenyl oxide were estimated. The hydrogenation/dehydrogenation reaction enthalpy of diphenyl oxide was calculated and compared with the data for other potential liquid organic hydrogen carriers.