Please use this identifier to cite or link to this item: https://hdl.handle.net/10216/100551
Author(s): Manuel J S Monte
Goncalves, MV
Maria D M C R Ribeiro da Silva
Title: Vapor Pressures and Enthalpies of Combustion of the Dihydroxybenzoic Acid Isomers
Issue Date: 2010
Abstract: The Knudsen mass-loss effusion technique was used to measure the vapor pressures at different temperatures of the following dihydroxybenzoic acids: 2,3-dihydroxybenzoic acid, between (345.22 and 363.18) K; 2,4-dihydroxybenzoic acid, between (376.22 and 392.11) K; 2,5-dihydroxybenzoic acid, between (372.14 and 388.92) K; 2,6-dihydroxybenzoic acid, between (347.14 and 365.17) K; 3,4-dihydroxybenzoic acid, between (387.12 and 403.26) K; and 3,5-dihydroxybenzoic acid, between (345.22 and 363.18) K. From the temperature dependences of the vapor pressure of the crystalline compounds, the standard (p(0) = 10(5) Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. For each of the six isomers the standard (p(0) = 0.1 MPa) molar enthalpy of formation in the crystalline phase was derived from the experimental standard molar energy of combustion, in oxygen, measured by static-bomb combustion calorimetry at T = 298.15 K. The combination of the standard molar enthalpy of formation in the crystalline phase with the standard enthalpy of sublimation yields the standard molar enthalpy of formation in the gaseous phase of the studied compounds.
Subject: Química física, Engenharia química
Physical chemistry, Chemical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia química
Engineering and technology::Chemical engineering
URI: https://repositorio-aberto.up.pt/handle/10216/100551
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FCUP - Artigo em Revista Científica Internacional

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