Standard Entropy Of Formation Research Articles

The thermodynamic functions of fullerene derivative (t-Bu)12C60 over the temperature range from T → 0 to 420 K

The temperature dependence of heat capacity C o = f(T) of fullerene derivative (t-Bu)12C60 has been measured by a adiabatic vacuum calorimeter over the temperature range T = 6–350 K and by a differential scanning calorimeter over the temperature range T = 330–420 K for the first time. The low-temperature (T ≤ 50 K) dependence of the heat capacity was analyzed based on Debye’s the heat capacity theory of solids and its fractal variant. As a consequence, the conclusion about structure heterodynamicity is given. The experimental results have been used to calculate the standard thermodynamic functions C o (T), H o(T)−H o(0), S o(T) and G o(T) − H o(0) over the range from T → 0 to 420 K. The standard entropy of formation at 298.15 K of fullerene derivative under study was calculated. The temperature of decomposition onset of derivative was determined by differential scanning calorimetery and thermogravimetric analysis. The standard thermodynamic characteristics of (t-Bu)12C60 and C60 fullerite were compared.

Thermodynamic properties of tetrabutylammonium iodide and tetrabutylammonium tetraphenylborate

The heat capacities of crystalline tetrabutylammonium iodide (TBAI) and tetrabutylammonium tetraphenylborate (TBATPhB) were determined over the temperature range 5−350 K by adiabatic vacuum calorimetry, generally with an uncertainty of ±0.2%. The experimental data were used to calculate the standard thermodynamic functions of TBAI and TBATPhB, namely, the heat capacity C ( T ) p ° , enthalpy H°( T) − H°(0), entropy S°( T) and Gibbs function G°( T) − H°(0) at p° = 0.1 MPa for the range from T → 0 to T = 350 K. The standard entropy of formation Δ f S° TBAI and TBATPhB at T = 298.15 K was also determined. Thermodynamic characteristics of fusion and solid-state transition were determined by DSC, their comparison with literature data were carry out; numerical values of enthalpies and entropies of transitions were discussed in dependence of compounds composition.

Low-temperature heat capacity and thermodynamic functions of compounds with the composition Ba(A 2/3 III U1/3)O3 (AIII = Sc, Y)

The heat capacity of crystalline Ba(Sc2/3U1/3)O3 and Ba(Y2/3U1/3)O3 in the range 80–350 K was studied by adiabatic vacuum calorimetry, and the thermodynamic characteristics of these compounds were evaluated. Their standard entropies of formation at 298.15 K were calculated.

Thermodynamic properties of anhydrous smectite MX-80, illite IMt-2 and mixed-layer illite–smectite ISCz-1 as determined by calorimetric methods. Part I: Heat capacities, heat contents and entropies

The heat capacities of the anhydrous international reference clay minerals, smectite MX-80, illite IMt-2 and mixed-layer illite–smectite ISCz-1, were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 6 to 520 K (at 1 bar). The samples were chemically purified and Na-saturated. Dehydrated clay fractions <2 μm were studied. The structural formulae of the corresponding clay minerals, obtained after subtracting the remaining impurities, are K 0.026 Na 0.435 Ca 0.010 ( Si 3.612 Al 0.388 ) ( Al 1.593 Fe 3 + 0.184 Mg 0.228 Fe 2 + 0.038 Ti 0.011 ) O 10 ( OH ) 2 for smectite MX-80, K 0.762 Na 0.044 ( Si 3.387 Al 0.613 ) ( Al 1.427 Fe 3 + 0.292 Mg 0.241 Fe 2 + 0.084 ) O 10 ( OH ) 2 for illite IMt-2 and K 0.530 Na 0.135 ( Si 3.565 Al 0.435 ) ( Al 1.709 Fe 3 + 0.051 Mg 0.218 Fe 2 + 0.017 Ti 0.005 ) O 10 ( OH ) 2 for mixed-layer ISCz-1. From the heat capacity values, we determined the molar entropies, standard entropies of formation and heat contents of these minerals. The following values were obtained at 298.15 K and 1 bar: C p 0 (J mol −1 K −1) S 0 (J mol −1 K −1) Smectite MX-80 326.13 ± 0.10 280.56 ± 0.16 Illite IMt-2 328.21 ± 0.10 295.05 ± 0.17 Mixed-layer ISCz-1 320.79 ± 0.10 281.62 ± 0.15

Standard Gibbs energy of formation of Zn17Y2 and Zn12Y determined by solution calorimetry and measurement of heat capacity from near zero Kelvin

Abstract The thermodynamic properties of Zn17Y2 and Zn12Y were investigated by calorimetry. The standard entropies of formation at 298 K, were determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpies of formation at 298 K, were determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energies of formation at 298 K, were determined from these data. The results obtained are: (Zn17Y2) = – 23.53 ± 1.4 kJ · (mol of atoms)−1; (Zn17Y2) = – 3.05 ± 0.39 J · K−1 · (mol of atoms)−1; (Zn17Y2) = – 22.62 ± 1.4 kJ · (mol of atoms)−1; (Zn12Y) = – 23.89 ± 1.8 kJ · (mol of atoms)−1; (Zn12Y) = – 0.78 ± 0.41 J · K−1 · (mol of atoms)−1; (Zn12Y) = – 23.66 ± 1.8 kJ · (mol of atoms)−1. The electronic contribution to the heat capacity of Zn17Y2 and Zn12Y is found to be similar to pure zinc, indicating that the valence electrons of yttrium in the compound are trapped by the density of states for zinc.

Thermodynamic Properties of AlNd Determined by Low Temperature Heat Capacity Measurements

The thermodynamic properties of AlNd were investigated by measuring the heat capacity, Cp, from near absolute zero (2 K) to 300 K using the relaxation method. During the measurement of the Cp(AlNd), 4 thermal anomalies were found on the Cp curve at 75.34, 39.79, 25.77, and 6.95 K. The third law entropy of AlNd at 298 K was obtained by integrating the polynomials for the measured Cp values. The result was as follows: S 298 (AlNd)/J·K -1 ·mol -1 = 93.72 ± 0.47. Using this value, the standard entropy of formation at 298 K was obtained as follows: Δ f S° 298 (AlNd)/J·K -1 ·mol -1 = -6.18±0.94.

Thermodynamics of Ba2Sm2/3UO6

The standard enthalpy of formation of crystalline Ba2Sm2/3UO6 at 298.15 K, −3040.0±7.5 kJ mol−1, was determined by reaction calorimetry. The heat capacity of the compound in the range 80–300 K was measured by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. Its standard entropy of formation at 298.15 K is −592.5±1.0 J mol−1 K−1, and the Gibbs energy of formation at 298.15 K, −2863.5±8.0 kJ mol−1. The standard thermodynamic functions of the reactions of the Ba2Sm2/3UO6 synthesis were calculated and discussed.

Thermodynamics of lutetium uranosilicate

The standard enthalpy of formation of crystalline Lu(HSiUO6)3 · 10H2O at 298.15 K, −10668.0±16.0 kJ mol−1, and the standard enthalpy of its dehydration were determined by reaction calorimetry. The heat capacity of this compound in the range 80–300 K was measured by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. The standard entropy of formation at 298.15 K is −3812.9±1.2 J mol−1 K−1, and the standard Gibbs energy of formation at 298.15 K, −9531.0±16.5 kJ mol−1. The standard thermodynamic functions of the reactions of the synthesis of lutetium uranosilicate were calculated and discussed.

The thermodynamic properties of star-shaped fullerene-containing poly-N-vinylpyrrolidone

The temperature dependence of the heat capacity of star-shaped fullerene-containing poly-N-vinylpyrrolidone was studied over the temperature range 6–390 K by precision adiabatic vacuum and dynamic scanning calorimetry. The temperature intervals and thermodynamic characteristics of phase transitions were determined. The low-temperature dependence of the heat capacity of the substance was analyzed according to the Debye theory of the heat capacity of solids and its multifractal generalization. The data obtained were used to calculate the standard thermodynamic functions C p o (T),H o(T)-H o(0), S o(T), and G o(T)-H o(0) of fullerene-containing poly-N-vinylpyrrolidone from T → 0 to 390 K. The standard entropy of formation of the polymer from simple substances and the entropy of its synthesis from poly-N-vinylpyrrolidone and fullerite C60 at 298.15 K were calculated. The thermodynamic characteristics of fullerene-containing poly-N-vinylpyrrolidone are compared with those of the polymer-analogue without C60.

Thermodynamics of calcium uranosilicate

The standard enthalpy of formation at 298.15 K of crystalline α-Ca(HSiUO6)2 · 5H2O (−6781.0 ± 9.5 kJ mol−1) was determined by reaction calorimetry. The heat capacity in the range of 80–300 K was measured by adiabatic vacuum calorimetry, and the thermodynamic functions of this compound were evaluated. The standard entropy of formation (−1978.6±1.2 J mol−1 K−1) and the Gibbs free energy of formation (6191.0±10.0 kJ mol−1) at 298.15 K were calculated. The standard thermodynamic functions of reactions of calcium uranosilicate synthesis were analyzed.

Standard Gibbs Energy of Formation of Zn&lt;SUB&gt;8&lt;/SUB&gt;La Determined by Solution Calorimetry and Measurement of Heat Capacity from Near Absolute Zero Kelvin

The thermodynamic properties of Zn 8 La were investigated by calorimetry. The standard entropy of formation at 298 K, Δ f S 298 , was determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, Δ f H 298 , was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, Δ f G 298 , was determined from these data. The results obtained were as follows: Δ f H 298 (Zn8La)/kJ·mol -1 =-297.18 ±18; Δ f S 298 (Zn 8 La)/J·mol -1 ·K -1 = -25.02±3.60; Δ f G 298 (Zn 8 La)/kJ·mol -1 =-289.71 ± 18. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn 8 La was small, indicating that decrease of the density of states for 4f component of the lanthanum atom in the vicinity of E F .

Standard molar entropies, standard entropies of formation, and standard transformed entropies of formation in the thermodynamics of enzyme-catalyzed reactions

The standard transformed Gibbs energy of reaction provides the criterion for spontaneous change and equilibrium for an enzyme-catalyzed reaction at specified temperature, pressure, and pH. The standard transformed enthalpy of reaction yields the heat of reaction. The standard transformed entropy of reaction has received less attention, but it provides almost all of the pH dependence of the apparent equilibrium constant. When the standard Gibbs energies of formation Δ f G j ∘ ( 298 . 15 K , I = 0 ) and standard enthalpies of formation Δ f H j ∘ ( 298 . 15 K , I = 0 ) of the species of a reactant are known, the standard entropies of formation Δ f S j ∘ ( 298 . 15 K , I = 0 ) can be calculated. With the database BasicBiochemData2 and recent extensions, this can be done for about fifty reactants. However, standard molar entropies S m ∘ ( 298 . 15 K , I = 0 ) of species are of more interest because it may be possible to interpret their values and use them to estimate S m ∘ values for species for which Δ f H j ∘ are unknown. These estimates of S m ∘ of species for which Δ f G j ∘ values are known make it possible to obtain Δ f H j ∘ of species that can be used to calculate effects of temperature on standard transformed Gibbs energies of reactants and apparent equilibrium constants of enzyme-catalyzed reactions.

Standard gibbs energy of formation of Mg48Zn52 determined by solution calorimetry and measurement of heat capacity from near absolute zero kelvin

The thermodynamic properties of Mg48Zn52 were investigated by calorimetry. The standard entropy of formation at 298 K, Δf S 298 o , was determined from measuring the heat capacity, C p , from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, Δf H 298 o , was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, Δf G 298 o , was determined from these data. The obtained results were as follows: Δf H 298 o (Mg48Zn52)=(−1214±(300) kJ · mol−1;ΔfS 298 o (Mg48Zn52)=(−123±0.36) J · K−1 · mol−1; and Δf G 298 o (Mg48Zn52)=(−1177±(300) kJ · mol−1. The electronic contribution to the heat capacity of Mg48Zn52 was found to be approximately equal to pure magnesium, indicating that the density of states in the vicinity of the Fermi level follows the free electron parabolic law.

Calorimetric study of Zn13La

Abstract The thermodynamic properties of Zn13La were investigated by calorimetry. The standard entropy of formation at 298 K, ΔfS°298, was determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, ΔfH°298, was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, ΔfG°298, was determined from these data. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn13La was similar to the composition average of the values of pure Zn and La, indicating that the 5d- and 4f-electron states for La are localized in the vicinity of the Fermi energy level.

Thermodynamic Properties of Dibenzo-24-crown-8 in the Range from T → 0 to 500 K

The temperature dependence of the heat capacity of dibenzo-24-crown-8 in the range 6-500 K was measured by adiabatic vacuum and dynamic calorimetry with an accuracy of 0.2-0.5%. The physical transformations of the title compound occurring on its heating and cooling within the above temperature range were revealed and characterized. From the experimental data obtained for dibenzo-24-crown-8, its thermodynamic functions C4p0(T), H0(T) - H0(0), S0(T) - S0(0), and G0(T) - H0(0) were calculated for the range from T → 0 to 500 K; the standard entropy of formation from the elements, ΔsS0, at T 298.15 K was also calculated. The fractal dimensions D in the heat capacity function of the multifractal version of the Debye heat capacity theory, characterizing the heterodynamic characteristics of the title compound, were calculated.

Calorimetric Study of Nickel Molybdate: Heat Capacity, Enthalpy, and Gibbs Energy of Formation

AbstractFor Abstract see ChemInform Abstract in Full Text.

Calorimetric Study of Nickel Molybdate: Heat Capacity, Enthalpy, and Gibbs Energy of Formation

The thermodynamic properties of the α and β polymorphs of NiMoO4 were directly investigated by calorimetry. The standard entropies of formation, ΔfS°T, of α and β were determined from measuring the molar heat capacity, Cp,m, from near absolute zero (2 K) to high temperature (1380 K) by a relaxation method and differential scanning calorimetry. The standard enthalpies of formation, ΔfH°T, of α and β were determined by combining Cp,m with the standard enthalpy of formation, ΔfH°298, at 298 K obtained from drop solution calorimetry in molten sodium molybdate at 973 K. The standard Gibbs energies of formation, ΔfG°T, of α and β were determined from their ΔfS°T and ΔfH°T values. The ΔfG°T values indicate that the polymorphic transformation from α to β occurs at 1000 K, consistent with the observed phase transformation at 1000 K.

Calorimetric study of MgZn2and Mg2Zn11

Abstract The thermodynamic properties of MgZn2 and Mg2Zn11 were investigated by calorimetry. The standard entropies of formation at 298 K, ΔfSo298, were determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 390 K by the relaxation method. The standard enthalpies of formation at 298 K, ΔfHo298, were determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energies of formation at 298 K, ΔfGo298, were determined from these data. The electronic contribution to the heat capacities of MgZn2 and M2Zn11 were found to be similar to pure Zn, indicating that the valence electrons of Mg are trapped by the density of states for Zn in the vicinity of the Fermi level.

Regularities in thermodynamic properties of interoxide polymeric compounds

It is shown that in terms of the number N of elements in solid interoxide polymeric compounds and minerals, the molar heat capacity ratio C /N is a p single function of temperature. The molar heat capacity of a solid polymeric compound is found to be equal to the sum of the molar heat capacities of its constituent solid oxides at all temperatures. The standard entropies of formation of the alkali and alkaline earth polymeric compounds per atom of oxygen are both-95±5 J [atom O]- 1 K-1, which is similar to all other inorganic compounds. The standard free energies and enthalpies of formation of polymeric interoxide compounds at a given temperature T are directly proportional to the number N of elements in the compound.

Heat capacity of copper hydride

The heat capacity of copper hydride has been measured in the temperature range 2–60 and 60–250 K using two adiabatic calorimeters. Special procedure for the purification of CuH has been applied and a careful analysis of sample contamination has been performed. The experimental results have been extrapolated up to 300 K due to instability of the copper hydride at room temperature. From the temperature dependence of heat capacity the values of entropy S°( T), thermal part of enthalpy H°( T)− H°(0) and Gibbs function [−( G°( T)− H°(0))] have been calculated assuming S°(0)=0. The standard absolute entropy, standard entropy of formation from the elements and enthalpy of decomposition of copper hydride from the elements have been calculated and found to be 130.8 J K −1 mol −1 (H 2), −85.1 J K −1 mol −1 (H 2), −55.1 kJ mol −1 (H 2), respectively. These new results gave the possibility of discussion on thermodynamic properties of copper hydride. Debye temperature has been for the first time determined experimentally.