The Eighteenth National days of Chemistry JNC 18, Monastir 21-23 Déc Viscosity Arrhenius activation energy and different properties in N,N-dimethylacetamide + Formamide systems at different temperatures. M. Dallela, M. Hichrib, E.S. Bel Hadj Hmidac, D. Dasd, M.A. Alkhaldie, N. Ouerfellia,e. a) Université de Tunis El Manar, Laboratoire Biophysique et de Technologies Médicales LR13ES04, Institut Supérieur des Technologies Médicales de Tunis, 9 Avenue Dr. Zouhaier Essafi 1006 Tunis, Tunisie.; b) Université de Tunis El Manar, Faculté des Sciences de Tunis, LR01SE10, Laboratoire de Thermodynamique Appliquée, Département de Chimie, 2092 Tunis, Tunisie. c) Laboratoire de Chimie Analytique et Electrochimie, Département de Chimie, Faculté des Sciences de Tunis, Campus Universitaire, 2092 El Manar, Tunisie. d) Department of Chemistry, Dinhata College, North Bengal University, Dinhata-736135, Cooch-Behar, West Bengal, India.; e) University of Dammam, Department of Chemistry, College of Science, P.O. Box 1982, Dammam 31441, Saudi Arabia.; Abstract Excess properties calculated from the literature values of experimental density and viscosity in N,N-dimethylacetamide + formamide binary mixtures between 298.15 K and 318.15 K can lead us to test different correlation equations as well as their corresponding relative functions. Inspection of the Arrhenius activation energy Ea and the enthalpy of activation of viscous flow ΔH* shows very close values. Here, we can define partial molar activation energies Ea1 and Ea2 for N,N-dimethylacetamide and formamide, respectively, along with their individual contribution separately. Correlation between the two Arrhenius parameters of viscosity in all compositions shows the existence of two main distinct behaviors separated by the mole fraction equal to 0.3 of N,N-dimethylacetamide. In addition, the correlation between Arrhenius parameters reveals interesting Arrhenius temperature, which is closely related to the vaporization temperature in the liquid vapor equilibrium and the limiting corresponding partial molar properties can permit us to predict the boiling points of the pure components. Results Figure 2. Arrhenius activation energy Ea/(kJ·mol−1) for {N,N-dimethylacetamide (1) + formamide (2)} mixtures in the temperature range (298.15– 318.15 K) as a function of the Logarithm of the entropic factor of Arrhenius Ln(As)(Pa.s) Figure 3. Arrhenius activation energy Ea/(kJ·mol -1) and partial molar activation energies of viscosity ( Eai/(kJ·mol−1) for {N,N-dimethylacetamide (1) + formamide (2)} mixtures as a function of the mole fraction of N,N-dimethylacetamide (x1) over the temperaturerange (298.15–318.15) K. (●): Ea(x1); (○): Ea1 (x1) and; (▲): Ea2 (x1). Figure 1. Logarithm of the entropic factor of Arrhenius, −R·ln(As) and entropy of activation of viscous flow ΔS* for DMA (1) and FA (2) mixtures vs. the mole fraction x1 of N,N-dimethylacetamide in the temperature range (298.15– 318.15 K). (●): −R·ln(As/Pa·s)/(J·K -1 ·mol -1); (○): ΔS*/kJ·mol -1. Figure 4. Correlation between the partial molar Arrhenius activation energies Ea1 (x1) and Ea2 (x1) for {N,N-dimethylacetamide (1) + formamide (2)}mixtures over the temperature range (298.15–318.15) K. Figure 5. Correlation between the partial molar quantities relative to the activation energies Eai/ (kJ·mol -1) and the logarithm of the entropic factors of Arrhenius − R·ln(Asi/Pa·s)/(J·K -1 ·mol -1) for {N,N-dimethylacetamide (1) + formamide (2)} mixtures over the temperature range (298.15–318.15) K. (●): Ea1 (x1) vs. − R·ln(As1) and, (○): Ea2(x1) vs. − R·ln(As2). Table 1. Comparison between the current Arrhenius temperature (TAi)/K for (xi≈ 1) and the corresponding boiling temperature Tbi/K of the pure component (i) in some binary mixtures. Conclusion Based on the same experimental data of dynamic viscosities and densities of DMA + FA binary mixtures at 298.15, 308.15 and 318.15 K [4,9] and at the atmospheric pressure, some new theoretical (semi-empirical) approaches have been reported, for improving investigations of variation of Arrhenius activation energy and derived partial molar properties against molar fraction composition. Arrhenius parameters of pure components (FA and DMA) are determined as a function of temperature. Correlation between the two Arrhenius parameters for binary mixtures permits us to reveal the viscosity Arrhenius temperature which characterizes the studied binary liquid mixture and can provide information on the vaporization temperature of the isobaric liquid–vapor equilibrium. Also, this correlation can give evidence of the existence of distinct composition regions with different behaviors. Thus, assuming that the activation energy is a thermodynamic quantity, we have determined the partial molar activation energy to release the individual interaction’s contributions of each pure component within the mixture for each well-defined composition. Also, the variation of logarithm of the Arrhenius entropic factor deviation against mole fraction (x1) of DMA shows the presence of minimum and maximum at two molar fractions, which was explained by the complex formation between DMA and FA [4]. Correlation between the partial molar quantities relative to the activation energies and the logarithm of the entropic factors of Arrhenius for DMA + FA mixtures over the temperature range can give an approximately linear behavior, i.e. no observable change in curvature. This quasi-straight line behavior suggests us to make an empirical equation by introducing a new parameter TA denoted as viscosity Arrhenius temperature that characterizes each binary system. In the case of molar quantities, we consider that the Arrhenius temperature (TA) is no longer a constant over the whole range of composition. We introduce a new concept of the Arrhenius’ current temperature (TAi) for each pure component (i) to find its value at the two extreme positions, i.e. at very high concentration and very high dilution, respectively. The results derived in the studied binary system gives an interesting fact that the isobaric boiling point (Tbi) of the pure components is very close or strongly depends upon the viscosity Arrhenius’ current temperature (TAi). In conclusion, we can ascertain that with more mathematical manipulations, we will be able to reveal some physical meanings of the viscosity Arrhenius parameters and it definitely develops as well as improves the thermodynamic theories and also to predict some information on liquid–vapor diagram through the study of the viscosity against temperature and composition only in the liquid phase of binary mixture. We can add that an additional study on the eventual relationship between the Arrhenius temperature and the properties of numerous binary mixtures can demonstrate how the method predicts the properties of other non-treated fluid mixtures. In order to firmly establish the utility of the Arrhenius temperature and develop a means for estimating such quantities, more mixtures will be studied in future to give a more clear discussed protocol. To our knowledge, there is no stronger theoretical and physical basis of this study or any developed predictive techniques for our initial assumptions and so we cannot able to provide more clearly our verifications. We are very much hopeful that these original and interesting experimental findings can be well received by the theorists for developing new theoretical approaches. Also, in a future work, we will address the effect of pressure on the viscosity and how correlation can be deduced with the theories already available.