Vapour pressures and the enthalpies and entropies of sublimation of five dicarboxylic acids

• Type: Article in International Scientific Journal
• Date: 1999

Authors

da Silva, MAVR (Author) FCUP; Monte, MJS (Author) FCUP; Ribeiro, JR (Author) Other

Journal

Title: Journal of Chemical Thermodynamics

Vol. 31

Pages: 1093-1107

ISSN: 0021-9614

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 79 Citations

Scopus - 81 Citations

Scientific classification

FOS: Engineering and technology > Mechanical engineering

Other information

Authenticus ID: P-001-3R2

DOI: 10.1006/jcht.1999.0522

Abstract (EN): The Knudsen mass-loss effusion technique was used to measure the vapour pressures of five crystalline dicarboxylic acids as a function of temperature. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation were derived by using the Clausius-Clapeyron equation and the standard molar entropies of sublimation were calculated. The standard molar enthalpies and entropies of sublimation at T = 298.15 K were also calculated by using the estimated value of the standard molar heat capacity of sublimation Delta(cr)(g)C(p,m)(O), = -50 J K-1 mol(-1): [GRAPHICS] The sublimation enthalpy increments for a CH2 group in straight-chain dicarboxylic acids with less than nine methylene groups were calculated as (7.9 +/- 0.4) kJ.mol(-1). The available values for the enthalpies of sublimation of straight-chain dicarboxylic acids with more than eight methylene groups are discussed in terms of partial cyclization. The standard molar enthalpies of formation of dicarboxylic acids in the gaseous phase have been derived. (C) 1999 Academic Press.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15