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Article Dans Une Revue The Journal of physical chemistry Année : 2007

Heat Capacity of Associated Systems. Experimental Data and Application of a Two-State Model to Pure Liquids and Mixtures

Résumé

The predictions from a recently reported (J. Chem. Phys. 2004, 120, 6648) two-state association model (TSAM) have been tested against experimental data. The temperature, T, and pressure, p, dependence of the isobaric heat capacity, Cp, for three pure alcohols and the temperature dependence at atmospheric pressure of the excess heat capacity, , for four alcohol + ester mixtures have been measured. The branched alcohols were 3-pentanol, 3-methyl-3-pentanol, and 3-ethyl-3-pentanol, and the mixtures were 1-butanol and 3-methyl-3-pentanol mixed with propyl acetate and with butyl formate. These data, together with literature data for alcohol + n-alkane and alcohol + toluene mixtures, have been analyzed using the TSAM. The model, originally formulated for the Cp of pure liquids, has been extended here to account for the of mixtures. To evaluate its performance, quantum mechanical ab initio calculations for the H-bond energy, which is one of the model parameters, were performed. The effect of pressure on Cp for pure liquids was elucidated, and the variety of (T) behaviors was rationalized. Furthermore, from the Cp data at various pressures, the behavior of the volume temperature derivative, (∂V/∂T)p, was inferred, with the existence of a (∂V/∂T)p versus T maximum for pure associated liquids such as the branched alcohols being predicted. It is concluded that the TSAM captures the essential elements determining the behavior of the heat capacity for pure liquids and mixtures, providing insight into the macroscopic manifestation of the association phenomena occurring at the molecular level.

Dates et versions

hal-00339084 , version 1 (16-11-2008)

Identifiants

Citer

Claudio A. Cerdeirina, J. Troncoso, D. Gonzalez-Salgado, Gonzalo Garcia-Miaja, Gérardo O. Hernandez-Segura, et al.. Heat Capacity of Associated Systems. Experimental Data and Application of a Two-State Model to Pure Liquids and Mixtures. The Journal of physical chemistry, 2007, 111 (5), pp.1119-1128. ⟨10.1021/jp0640272⟩. ⟨hal-00339084⟩
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