DENSITY AND VISCOSITY MEASUREMENTS OF AQUEOUS SOLUTIONS OF 2 METHOXYETHANOL AT TEMPERATURES (298.15, , , AND ) K

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1 Journal of Al-Nahrain University Vol.(3), December, 008, pp.-7 Science DNSITY AND VISCOSITY MASURMNTS OF AQUOUS SOLUTIONS OF MTHOXYTHANOL AT TMPRATURS (98.5, 303.5, 308.5, AND 33.5) K Taghried A. Salman Department of Chemistry, College of Science, Al- Nahrain University. Abstract Densities and viscosities have been measured for the binary mixtures of methoxyethanol ( M) and water at 98.5, 303.5, and 33.5 K. From the precise density measurements, the excess molar volume ( V ) were calculated, V results are negative over the entire range of mole fractions and become less negative as the temperature increases. The deviation in viscosity (Δη) and excess molar Gibbs free energy of activation of viscous flow (ΔG * ) have been calculated from experimental viscosity measurements at different temperatures. ηδ and ΔG * data are positive over the whole mole fraction range. The observed results of V, ηδ and ΔG * are discussed in terms of molecular interactions in these binary mixtures. Generally, molecular interactions dominant these behaviors are of type, disruption and formation of intra and interhydrogen bonding between like and unlike molecules, respectively and dipole dipole interaction. The experimental excess functions V, ηδ and ΔG * were fitted to the Redlich Kister polynomial equation to evaluate the adjustable parameters and standard deviation from ideality. Introduction -Methoxyethanol is the first member of alkoxyalkanols and used extensively as solvent and solublizing agent in many industries with interests ranging from pharmaceutical to plastic products. From theoretical point of view, it is very interesting molecule having the ability to form intra and intermolecular hydrogen bonds. On the other hand, alkanols (alcohols) are the most well known solvents with protic and self associated properties. Methoxyethanol, an ether alkanol, shows physiochemical characteristic midway between protic and dipolar aprotic solvents (). Studies on excess functions of binary liquid mixtures are of considerable importance in understanding the nature of molecular interactions that determined by intermolecular forces (hydrogen bonding, charge transfer complex, Van der Waals forces, etc.) (,3). To determine the extent and type of interactions between M and water molecules, the densities and viscosities of binary mixtures of -M with water have been measured. xperimental Methoxyethanol (CH 3 OCH CH OH) was obtained from Aldrich Chemical Company, with purity > 99 %. The solvent was kept on activated molecular sieves type 4 A o for 4 hours then filtered before use. Bidistilled deionized water, its conductivity ( s.cm ) was used. The experimental measured values of density, ρ and viscosity η for both solvents are agreed well with those values published in the literature (4-8), Table ().

2 Taghried A. Salman Table () Comparison of Densities, ρ, and Viscosities, η, of Pure Components with Literature Data at 98.5 K. Component ρ/ g.cm -3 η/ cp Obs. Lit. Obs. Lit. Methoxyethanol (4) (8) (7) (6) (6).54 (7) Water (6) (7) (6) (5) All mixtures were prepared by using determined volumes to obtain samples covering the whole range of mole fraction (0 > x > ). Mixtures were kept in air tight stoppered bottle to revent any contamination. The possible error in mole fraction is estimated to be less than ± 0 4. Densities of pure liquids and their mixtures were determined using a digital densimeter (Anton paar DMA 60/ 60), the density values were reproducible to within 0 5 g.cm 3. On the other hand, the viscosity of pure liquids and binary liquid mixtures were measured using a Schot Gerate (AVS 300) viscometer thermostated with a digital water bath (T 500). The flow times were determined electronically with an electric timer of precision ±0.0 s. The accuracy in the measurements of viscosity was ± 0.00 mpa.s. Results and Discussion The experimental results for the density (ρ) of the aqueous solution of M at 98.5, 303.5, and 33.5 K are listed in Table (). The excess molar volume, V, was calculated from the following equation (9) : where x, x, M, M, ρ and ρ represent the mole fraction, molecular weight and the density of the pure component liquids and respectively. ρ is the density of the mixture. xcess molar volumes calculated from eq. are listed in Table (). The experimental results for the viscosity (η) are presented in Table 3. Fig. () showed the variation of viscosity as a function of the mole fraction of M, this figure show maxima at about mole fraction of M. The viscosity deviations, ηδ are obtained by: / cp x x... (3) where η is the viscosity of the mixture and x, η and x, η are the mole fraction and viscosity of pure components and, respectively. The viscosity deviation, Δη, at 98.5, 303.5, and 33.5 K are presented in Table (3). ηδ is plotted as a function of M mole fraction, Fig. (3). ηδ values are positive as the temperature increases with maxima at about 0.35 mole fraction of M. V m /(cm 3 mol ) X M X M X M X M...()

3 V / cm. mol 3 - Journal of Al-Nahrain University Vol.(3), December, 008, pp.-7 Science Table () Densities ρ, and xcess Molar Volumes, V for binary mixtures of x M + x water at different temperatures. X T=98.5 K T=303.5 K ρ/g.cm -3 V /cm 3.mol - ρ/g.cm -3 V /cm 3.mol X T=308.5 K T=33.5 K ρ/g.cm -3 V /cm 3.mol - ρ/g.cm -3 V /cm 3.mol x Fig. () : xcess molar volumes, V, for (x M + x water) versus x at different temperatures: ( ) 98.5; ( ) 303.5; ( ) 308.5; ( ) 33.5 K. 3

4 Taghried A. Salman Table (3) Viscosities η, Viscosity deviations, ηδ, and xcess Molar Gibbs free energy of activation of viscous flow, ΔG * for binary mixtures of x M + x water at different temperatures. T=98.5 K T=303.5 K X η/cp Δη /cp ΔG * / kj.mol - η/cp Δη /cp ΔG * / kj.mol T=308.5 K T=33.5 K X η/cp Δη /cp ΔG * / kj.mol - η/cp Δη /cp ΔG * / kj.mol /cp.0.5 /cp x Fig.() : Viscosity, η, of (x M + x water) versus x at different temperatures: ( ) 98.5; ( ) ( ); 308.5; ( ) 33.5 K x Fig. (3) : xcess Viscosity, Δη, of (x M + x water) versus x at different temperatures: ( ) 98.5; ( ) 303.5; ( ) 308.5; ( ) 33.5 K. 4

5 Journal of Al-Nahrain University Vol.(3), December, 008, pp.-7 Science The excess molar Gibbs free energy of activation of viscous flow, ΔG *, have been calculated from density and viscosity data according to the equation (0) : G RT ln m Vm x ln V x ln V... (4) where x and x are the mole fraction of M and water respectively. η m, η and η are the viscosity of mixture, M and water respectively.v m, V, and V are the molar volume of mixture, M and water respectively. The calculated ΔG * values are given in Table (3). For the mixture studied, the ΔG * values are positive over the whole mole fraction range at all temperatures as shown in Fig.(4). G * / kj. mol The calculated values of V, ηδ and ΔG * were fitted to a Redlich Kister polynomial equation () : n Y x x A j (x x ) j... (5) j0 where Y the excess property, V, ηδ or ΔG * and n is the number of adjustable parameters A j in each case for all mixtures, the optimum number of adjustable parameters is ascertained from an examination of the variation in standard deviation, σ, as given by () / Yobs Y (Y ) cal... (6) N P where N represent the number of experimental points and P the number of adjustable parameters. The values of these parameters, A j, along with the standard deviation, σ are listed in Table (4) x Fig. (4) : xcess activation energy of viscous flow, Δ G *, of (x M + x water) versus x at different temperatures: ( ) 98.5; ( ) 303.5; ( ) 308.5; ( ) 33.5 K. Table (4) Redlich Kister coefficients A j and Standard deviation, σ for the excess molar quantities of solution of (x M + x water) at different temperatures. Property T/K A o A A σ V /cm 3.mol Δη /cp ΔG * 98.5 / kj.mol

6 Taghried A. Salman xcess molar volumes (V ) are negative over the entire range of mole fractions and become less negative as the temperatures increases Fig.(). Fig.() shows that the minimum lies at a mole fraction of about 0.35 M. Many effects may contribute to the negative value of V. These effects are the disruption of (i) intramolecular hydrogen bonding of M and H O themselves (ii) intramolecular dipolar interaction in methoxyethanol (iii) the possible formation of hydrogen bond interactions between M and H O and (iv) the interstitial accommodation of the component into the other. Many studies in the literature (3-5) on water and M mixture agree with our present results are indicated that intramolecular hydrogen bonding exists in M in the liquid state. Moreover, the values of the Kirkwood correlation factor, g k (give an idea about the intermolecular forces between the solution contents through the dielectric constant measurements) (6,7), for pure M in the temperature range 5, 35, and 45 o C are not much greater than unity (the g k of M are.483,.478, and.463, respectively). These values indicated that M is relatively, unstructured liquid having strong but not specific dipole dipole interaction. Fig.() shows that the Δη values of mixtures of M and water are positive over the whole mole fraction range at all temperatures passes through a maxima at a mole fraction of 0.35 M which also gives an indication of the presence of specific interaction between M and water molecules, supports the V behavior (8,9). On the other hand, the Δ G * values was also positive, the positive deviation from ideality of Δη and Δ G * for mixture were attributed to the larger and positive interaction effect of M and H O that also supports the results obtained for V. References [] T.L.Ionic,. "Densities and Refractive Indices of the Binary Mixtures Containing Methanol, thanol,,-thanediol, and - Methoxyethanol at 98.5 K. " J.Chem.Soc.Faraday Trans., Vol.89, No.,993, pp [] A.Marchetti and L.Tassi, "Denities and xcess Molar Volumes of the Solvent (thane-,-diol + -Methoxyethanol + Water) from T = 63.5K to T= 353.5K", J. Chem. Thermodyn. Vol.30, No 5, 998, pp [3] C. Coquelet, A. Valtz, X. Courtial, D. Richon, "xcess Molar Volumes of Binary Mixtures of N, N-Dimethylformamide with Water at Temperatures from 77.3 to 38.5 K", Thermochim. Acta, Vol.448, No., 006, pp [4] L.Albuquerque, C.Ventura and R.Goncalves, "Densities and Volumetric Properties of -Methoxyethanol with N,N-Dimethylformamide and Water at Different Temperatures", J. Mol. Liq. Vol. 3, No. 30, 006, pp [5] M.A.Rubio, J.A.Gonzalez, and J.C.Cobos, "Physiochemical Properties of a Binary Mixtures of Water +,-thanediol, +- Methoxyethanol,+-thoxyethanol, and -butoxyethanol at K", J.Chem. ng. Data, Vol. 43, No., 000, pp [6] T.M.Aminabbavi, and B.Gopalakrishna, "Density, Viscoity, and Refractive Index of Binary Mixtures of Water with N,N- Dimethylformamide, Dimethylsulfoxide, -Methoxyethanol at 98.5 K", J. Chem. ng. Data, Vol.40, No., 00, pp [7] B.Das and D.Hazra, "xcess Molar Volumes of Binary Mixtures of -Methoxyethanol + Water at Different Temperatures",J. Chem. ng. Data, Vol.38, No.3 003, pp [8] M. N. Roy, B. Sinha, and V. K. Dakua, "Liquid-Liquid quilibria Data for -Methoxyethanol or -thoxyethanol + Dodecane",J. Mol. Liq. Vol.36, No., 007,pp [9].Jimenez, C. Franjo, and M. I. PazAndrade, "Densities and xcess Molar Volumes of Binary Mixtures Containing Isobutyl alcohol, thanol, and -Methylpentene at 98.5 K", J. Chem. ng. Data, Vol.4, No., 997, pp [0] G.Delmas, P.Parves, P. dest Romian, "Densities and Viscosities of Binary Mixtures of N-Formylmorpholine and an 6

7 Journal of Al-Nahrain University Vol.(3), December, 008, pp.-7 Science Aromatic Hydrocarbon", J.Phys. Chem., Vol.79, No., 998, pp [] O.Redlich and A. T. Kister, "Algebric Representation of Thermodynamic Properties and the Classification of Solutions", Ind. ng. Chem., Vol.40, No.3 948, pp [] F. Kohler, "Physical and Thermodynamic Properties of Pure Chemicals", Data Compilation,Monatsh. Chem., Vol.9, No., 960, pp [3] G.Douheret and A. J. Pal, "xcess Molar Volumes, xcess Viscosities, and xcess Activation nergies of Viscous flow for -Methoxyethanol + Water and + Sulfolane at K", J. Chem. ng. Data, Vol.7, No., 988, pp [4] G.Roux, G. Perron, and J.. Desnoyers, "AThermodynamic Investigation of Aqueous -Methoxyethanol",J. Chem. Thermodyn., Vol.5, No., 993, pp [5] G.Douheret, A. Pal, and M.I.Davis, "Viscometric and Volumetric Behavior of Binary Mixtures of -Methoxyethanol + Water at Different Temperatures". J.Chem. Thermodyn., Vol., No., 990, pp [6] H. Frohlich, "Theory of Dielectric", nd ed, Claredon press, 958, Oxford, U. K. pp [7] J. G. Kirkwood, "Dielectric Constant, Intermolecular Forces, and Optical Rotation of Organic Compounds", "J. Phys. Chem. ", Vol.84, No.3, 966, pp [8] M. Mazrul, M. Monirul, and M. N. Yeasmin, "Viscosity of Aqueous Solutions of -Methoxyethanol, -thoxyethanol. and thanolamine", J.Chem. Thermdyn. Vol. 36, No. 0, 004, pp [9] M.Cocchi, and A.Marchetti, "Kinematic Viscosities of Binary Mixtures Containing -Methoxyethanol and water from -0 o C to 80 o C, " Fluid Phase quilibria, Vol. 57, No., 999, pp الخالصة تم في هذا البحث قياس الكثافة و المزوجة لمحاليل ميثوكسي ايثانول + الماء الربعة درجات ح اررية و 33.5 كمفن و عمى مدى الكسر المولي. تم حساب الحجوم الموالرية الفائضة V من القيم العممية لمكثافات و لقد وجد ان هذه القيم تنحرف سمبا عن السموك المثالي عمى المدى الكامل من الكسر المولي و يزداد النح ارف السالب كمما ازدت درجات الح اررة. باستخدام قيم المزوجة العممية تم حساب انح ارف المزوجة عن ΔG * المثالية ηδ و كذلك طاقة كبس الحرة الفائضة لممحاليل و عمى مدى المختمفة و لقد وجد ان قيم الكسور المولية و درجات الح اررة ηδ و ΔG * تنحرف ايجابا عن المثالية و يزداد هذا الشذوذ كمما ازدت درجة الح اررة. ΔG * باالعتماد عمى ميثوكسي و الماء ηδ و تم مناقشة نتائج V نوع التأثي ارت المتبادلة الحاصمة بين و التي تم تشخيصها عمى انها قد تكون تكسر و تكون االواصر الهيدروجينية الضمنية و البينية بين الجزيئات المتشابهة و المختمفة عمى التوالي او من نوع تأثر ثنائي القطب ثنائي القطب. تم تعيير القيم العممية لجميع الدوال الفائضة ηδ V و ΔG * باستخدام معادلة ردلخ كستر متعددة الحدود و تم ايجاد الحدود المتعددة لممعادلة و استخدام النتائج لحساب االنح ارف القياسي عن المثالية لهذه القيم. 7