The standard molar enthalpy of formation at 298.15 K of VS1.043 by combustion calorimetry in fluorine

doi:10.1016/0021-9614(87)90009-7

The Journal of Chemical Thermodynamics

Volume 19, Issue 12, December 1987, Pages 1325-1331

https://doi.org/10.1016/0021-9614(87)90009-7 Get rights and content

Abstract

The standard molar enthalpy of formation Δ_fH_m^o of VS_1.043 has been determined by fluorine-combustion calorimetry. The result obtained, −(230.3±2.2) kJ·mol⁻¹ at 298.15 K and p^o = 101.325 kPa, differs significantly from values deduced from high-temperature studies.

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A summary is reported on alloy thermodynamics with special reference to the measurements and evaluation of the formation enthalpies by means of calorimetric techniques. Also, advantages and drawbacks of direct and indirect reaction calorimetry are presented and discussed on the basis of the work in progress in the authors’ laboratory. Comments are finally made about the problems of the calibration, intercalibration and assessment of the thermochemical data. Importance is given to the peculiar difficulties of alloy thermochemistry and to the need for a strict determination of the composition (elemental and phase composition) of the sample and of its equilibrium state.
Thermodynamic properties of vanadium silicides. I. Standard molar enthalpy of formation Δ<inf>f</inf>H<sup>o</sup><inf>m</inf> of vanadium disilicide (VSi<inf>2</inf>) at the temperature 298.15 K
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The massic energy of combustion of vanadium disilicide in fluorine according to the reaction V Si₂(cr) + (13 / 2)F₂(g) = V F₅(g) + 2SiF₄(g) has been measured calorimetrically. On the basis of the derived molar enthalpy of reaction and the standard molar enthalpies of formationΔ_fH_m^o of VF₅(g) and SiF₄(g),Δ_fH_m^o (VSi₂, cr, 298.15 K) = − (133.3 ± 2.0)kJ · mol^− 1at T = 298.15 K and p = 0.1 MPa. This result is compared with other values ofΔ_fH_m^o (VSi₂) from the literature. The complete conventional thermodynamic properties of VSi₂are also tabulated between the temperatures 298.15 K and 1950 K.
Méthode d'estimation des enthalpies de formation et des enthalpies libres de formation des composés inorganiques
1992, Thermochimica Acta
A modified version of Wilcox's equation was used to estimate the enthalpies of formation (Δ_fH°) and free energy of formation (Δ_fG°) of binary inorganic compounds in the solid state. The Δ_fH° values of almost 4800 molecules and Δ_fG° values of about 2700 molecules were calculated. The maximum deviation between the calculated and the experimentally determined values was 15.4 kcal mol⁻¹. This work is being continued by extending the method to compounds containing several different anions and/or several cations.
Une version modifiée de la relation de Wilcox permet une estimation des enthalpies de formation (Δ_fH°) et des enthalpies libres de formation (Δ_fG°) des composés binaires inorganiques à l'état solide. La méthode a été appliquée à près de 4800 molécules pour le calcul de Δ_fH° et à environ 2700 molécules pour le calcul de Δ_fG°. L'écart maximal entre les valeurs calculées et expérimentales est de 15,4 kcal mol⁻¹. L'étude se poursuit par l'extension de la méthode aux composés dont la molécule renferme plusieurs anions et plusieurs cations différents.
Standard molar enthalpies of formation and transition at the temperature 298.15 K and other thermodynamic properties of the crystalline and vitreous forms of arsenic sesquiselenide (As<inf>2</inf>Se<inf>3</inf>). Dissociation enthalpies of AsSe bonds
1990, The Journal of Chemical Thermodynamics
Fluorine-combustion calorimetry was used to determine the standard molar enthalpies of formation (at the temperature 298.15 K and with standard pressure p^o = 101.325 kPa) of the crystalline and vitreous forms of arsenic sesquiselenide. The following results were obtained: Δ_fH_m^o(As₂Se₃, cr) = −(86.1±4.1) kJ·mol⁻¹ and Δ_fH_m^o(As₂Se₃, vit) = −(58.1±4.2) kJ·mol⁻¹. The enthalpy of the transition from the vitreous to the crystalline forms of As₂Se₃, −(28.0±3.9) kJ·mol⁻¹ at 298.15 K, is consistent with two of several published values for the enthalpy of fusion of the crystalline sesquiselenide. The present results have been combined with enthalpy increments and the standard entropy has been recalculated from the literature to give, for As₂Se₃(cr) only, Δ_fH_m^o and the standard molar Gibbs energy of formation Δ_fG_m^o as functions of temperature. Mean bond enthalpies have been deduced for As₄Se₃(g) and As₄Se₄(g) on the basis of the new Δ_fH_m^o values, and the thermodynamic results are shown to be consistent with a linear structure for As₂Se₂(g) with a central AsAs bond. Bond dissociation enthalpies D_m^o(As-X) are given, where X = O, S, Se, and Te.
Standard molar enthalpy of formation at 298.15 K of the β-modification of molybdenum ditelluride
1989, The Journal of Chemical Thermodynamics
Fluorine-combustion calorimetry of a high-purity sample of molybdenum ditelluride has yielded the standard molar enthalpy of formation: Δ_fH_m^o MoTe₂, cr, β, 298.15 K) = −(84.2 ± 4.6) kJ·mol⁻¹. At 298.15 K, the enthalpy of the hypothetical β-to-α transition in MoTe₂ is approximately −6 kJ·mol⁻¹. The present result for Δ_fH_m^o(MoTe₂) has been combined with literature values for the decomposition pressures of MoTe₂ to yield Δ_fH_m^o(Mo₃Te₄, cr, 298.15 K) = −(185 ± 10) kJ·mol⁻¹. Our previously published Δ_fH_m^o(TeF₆) (Trans. Faraday Soc. 1966, 62, 558) has been revised slightly to −(1371.8 ± 1.8) kJ·mol⁻¹.
Standard molar enthalpy of formation by fluorine-combustion calorimetry of tungsten diselenide (WSe<inf>2</inf>). Thermodynamics of the high-temperature vaporization of WSe<inf>2</inf>. Revised value of the standard molar enthalpy of formation of molybdenite (MoS<inf>2</inf>)
1988, The Journal of Chemical Thermodynamics
A high-purity sample of WSe₂, containing in total mass fraction less than 1 × 10⁻⁴ of oxygen and other impurities, has been synthesized by combination of the elements. The standard specific energy of combustion of pure WSe₂ in fluorine, as measured by high-precision calorimetry, is −(10993.7±15.0) J · g⁻¹, and the derived standard molar enthalpy of formation Δ_fH_m^o is −(185.3 ± 5.5) kJ · mol⁻¹ at T = 298.15 K and p^o = 0.101325 MPa. This result is compared with other literature values, and the equilibrium partial pressures of Se₂(g) and Se(g) are estimated for decomposition of WSe₂ to {W + Se₂(g)} and $12 WSe_{2}$ to ${12 W + Se(g)}$ . Our published result (J. Chem. Thermodynamics 1970, 2, 797) for Δ_fH_m^o(MoS₂) at 298.15 K has been revised to −(271.8 ± 4.9) kJ · mol⁻¹.

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^☆: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract W-31-109-Eng-38.

^b: Present address: Chemistry Department, University of Iowa, Iowa City, Iowa. Participant in Undergraduate Research Program at Argonne National Laboratory, coordinated by the Division of Educational Programs.

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The standard molar enthalpy of formation at 298.15 K of VS1.043 by combustion calorimetry in fluorine☆

Abstract

J. Chem. Thermodynamics

J. Chem. Thermodynamics

J. Chem. Thermodynamics

J. Chem. Thermodynamics

J. Chem. Thermodynamics

J. Chem. Thermodynamics

J. Chem. Thermodynamics

Rev. Met. (Paris)

Stal

J. Phys. C.

Rev. Chim. Miner.

Metall. Trans. B

J. Chem. Phys.

Fiz. Khim. Elektrokhim. Rasplav. Solei Shlakov

The standard molar enthalpy of formation at 298.15 K of VS_1.043 by combustion calorimetry in fluorine☆