Experimental study and ERAS modeling of the excess molar enthalpy of (acetonitrile + 1-heptanol or 1-octanol) mixtures at (298.15, 313.15, and 323.15) K and atmospheric pressure

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Abstract

As a continuation of our studies on excess functions of binary systems, experimental data of excess molar enthalpy (HmE) of (acetonitrile + 1-heptanol or 1-octanol) mixtures have been determined as a function of composition at (298.15, 313.15, and 323.15) K at atmospheric pressure using a modified 1455 PARR mixture calorimeter. The HmE is positive for both systems over the whole composition range. The applicability of the ERAS-Model to correlate HmE of the mixtures studied was tested. The agreement between experimental and calculated values is satisfactory.

Introduction

Experimental studies on excess molar properties, just as excess enthalpy (HmE) and excess volume (VmE), of (binary liquid alkanols + acetonitrile) containing mixtures have been performed to understand the molecular interactions between the components as well as to test the predictive or correlative capability of solutions models involving such polar compounds. Experimental VmE of {acetonitrile + alkanols (C1–C5 and C8)} mixtures at the temperature range (298.15 to 308.15) K and atmospheric pressure are reported by Narayanaswamy et al. [1], Cibulka et al. [2], Sandhu et al. [3], Aznarez and Postigo [4], and Dewan and Mehta [5]. Experimental HmE of {acetonitrile + alkanols (C1 and C3)} mixtures at 298.15 K and atmospheric pressure are reported by Nagata et al. [6] and Nagata and Tamura [7]. Experimental and modeling VmE and HmE of {acetonitrile + alkanols (C1–C6)} mixtures at the temperature range (288.15 to 323.15) K and atmospheric pressure are reported by Torres et al. [8], [9], [10], Pina and Francesconi [11], and Galvão and Francesconi [12]. In this work, excess molar enthalpy (HmE) values of (acetonitrile + 1-heptanol or 1-octanol) mixtures have been determined as a function of composition at 298.15, 313.15, and 323.15 K at atmospheric pressure. The applicability of the ERAS-Model [13] to correlate experimental HmE of these mixtures was tested.

Section snippets

Experimental

The reagent acetonitrile is analytical grade and was supplied by EM Science – Merck (USA, purity >99.99 mol%), 1-heptanol (Avocado Research Chemicals, purity >99 mol%), and 1-octanol (Aldrich, purity >99.5 mol%) were dried over molecular sieves (3 Å). In order to check the purity of the substances, density, and refractive index measurements were performed using a vibrating-tube densimeter (Anton Paar, DMA 55, resolution 1 × 10−5 g · cm−3) and an Abbé type refractometer (Atago, model 3T, resolution 1 × 10−4

Testing system

The performance of the calorimeter was tested by measuring HmE of the well-investigated system (ethanol + water) [16], [17], [18] at 298.15 K over the whole composition range and atmospheric pressure. A comparison between experimental data with the plentiful literature data taken from Costigan et al. [18] shows an average difference lower than 1.0% over the whole composition range.

(Acetonitrile + alkanols) systems

Measured HmE data for (acetonitrile + 1-heptanol or 1-octanol) as a function of the composition at 298.15, 313.15, and

Conclusion

Experimental HmE data of (acetonitrile + 1-heptanol or 1-octanol) containing mixtures were determined at (298.15, 313.15, and 323.15) K and atmospheric pressure. These data were correlated using the ERAS-Model [13]. The agreement between experimental and calculated values is satisfactory. Physical contributions (represented by equation (6)) are dominant in relation to chemical contributions (equation (7)). This can be confirmed by experimental HmE data which are large and positive. This behavior

Acknowledgements

Ricardo F. Checoni wishes to thank CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the financial support received in the form of a postgraduate fellowship and to express his gratitude to Prof. Jarbas J.R. Rohwedder and to Prof. Sergio P. Ravagnani for technical and academic assistance.

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