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Measurement and modeling of the excess molar enthalpy for water + amide mixtures from 288.15 K to 303.15 K and at atmospheric pressure


R. Checoni1 and P. Volpe2

1Universidade Estadual de Campinas - UNICAMP, Brazil
2Universidade Estadual de Campinas - UNICAMP, Brazil

Keywords: modeling, equation of state
property: excess molar enthalpy
material: water ∙ formamide ∙ N,N-dimethylformamide ∙ N,N-dimethylacetamide

Experimental data of excess molar enthalpy of binary mixtures containing water plus an amide (formamide, N,N-dimethylformamide or N,N-dimethylacetamide), as a function of composition, in the temperature range 288.15 K to 303.15 K and at atmospheric pressure have been determined calorimetrically. The excess molar enthalpy data are negative for aqueous solutions containing N,N-dimethylformamide or N,N-dimethylacetamide and positive for solutions containing water + formamide over the whole composition range. The results of the experimental data on the excess molar enthalpy are discussed in terms of the influence of the temperature and of the organic solvent type present in the binary aqueous mixtures as well as in terms of the existing molecular interactions and organic solvent molecular size and format. The excess molar enthalpy data are correlated using a model developed from an equation of state constituted of the sum of two terms: one related to molecular repulsions, developed by Carnahan-Starling [1] and one accounting for molecular attractions, similar to that proposed by Peng-Robinson [2]. In both terms, the adjustable parameters are temperature dependent. The results obtained from application of this model are in satisfactory agreement with the HEm experimental data of the aqueous mixtures studied.

References
  1. N.F. Carnahan, K.E. Starling, AIChE J. 18, 1184-1189 (1972)

  2. D-Y Peng., D.B. Robinson, Ind. Eng. Chem. Fundam. 15, 59-64 (1976)

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