Standard molar enthalpies of formation and transition at 298. 15 K and other thermodynamic properties of the crystalline and vitreous forms of arsenic sesquiselenide (As sub 2 Se sub 3 ): Dissociation enthalpies of As-Se bonds
Fluorine-combustion calorimetry was used to determine the standard molar enthalpies of formation (at 298.15 K and p{sup 0} = 101.325 kPa) of the crystalline and vitreous forms of arsenic sesquiselenide. The following results were obtained: {Delta}{sub f}H{sub m}{sup 0}(As{sub 2}Se{sub 3}, cr) = {minus}(86.1 {plus minus} 4.1) kJ{center dot}mol{sup {minus}1} and {Delta}{sub f}H{sub m}{sup 0}(As{sub 2}Se{sub 3}, vit) = {minus}(58.1 {plus minus} 4.2) kJ{center dot}mol{sup {minus}1}. The enthalpy of the transition from the vitreous to the crystalline forms of As{sub 2}Se{sub 3}, {minus}(28.0 {plus minus} 3.9) kJ{center dot}mol{sup {minus}1} at 298.15 K, supports 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 recalculated from the literature to give, for As{sub 2}Se{sub 3}(cr) only, {Delta}{sub f}H{sub m}{sup 0} and the standard molar Gibbs energy of formation {Delta}{sub f}G{sub m}{sup 0} as functions of temperature. Mean bond enthalpies have been deduced for As{sub 4}Se{sub 3}(g) and As{sub 4}Se{sub 4}(g) on the basis of the new {Delta}{sub f}H{sub m}{sup 0} values, and the thermodynamic results are shown to be consistent with a linear structure for As{sub 2}Se{sub 2}(g). Bond dissociation enthalpies D{sub m}{sup 0}(As--X) are given, where X = O, S, Se, and Te. 47 refs., 1 fig., 4 tabs.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5490148
- Report Number(s):
- CONF-880810-2; CONF-8809198-1; ON: DE90002260
- Resource Relation:
- Conference: 10. IUPAC conference on chemical thermodynamics; 4. Polish conference on calorimetry and thermal analysis, Prague (Czechoslovakia); Warsaw (Poland), 29 Aug - 2 Sep 1988; 4-10 Sep 1988
- Country of Publication:
- United States
- Language:
- English
Similar Records
Fluorine as an oxidant in combustion calorimetry
Thermochemistry of (germanium + selenium) : a review and critical assessment.