ULTRASONIC AND CONDUCTOMETRIC STUDIES OF NACL SOLUTIONS THROUGH ULTRASONIC PARAMETERS

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1 International Journal of Recent Innovation in Engineering and Research Scientific Journal Impact Factor by SJIF e- ISSN: ULTRASONIC AND CONDUCTOMETRIC STUDIES OF NACL SOLUTIONS THROUGH ULTRASONIC PARAMETERS Manoj Kumar Praharaj 1 1 Department of Physics, ABIT, BPUT, CDA-1, Cuttack, Odisha , India. Abstract- Ultrasonic velocity, density and viscosity have been measured for aqueous solution of NaCl at different temperatures and at constant frequency. These experimental data have been used to estimate the thermodynamic parameters such as Rao s constant, Wada s constant, surface tension and solvation number. The parameters were explained on the basis of intermolecular interaction present in the solution. Electrical conductivity was measured and along with the above parameters was used to study the ionicity of NaCl. Keywords ultrasonic, hydration, surface tension, solvation number, molecular interaction I. INTRODUCTION Ultrasonic studies provide a wealth of information about the state of liquids. The measurement of ultrasonic velocity in pure liquids and mixtures is an important tool to study the physiochemical properties of the liquids and also explain the nature of molecular interactions. Since ionic liquids are attracting growing interest as alternative to molecular liquids [1-2], it is important to study the various properties of ionic liquids through ultrasonic studies. Ionic liquids have been currently applied as novel solvents in organic synthesis [3-6], catalysis [7,8], electro chemistry [9] and chemical separation [10]. The present work investigates, thermo-dynamical properties of aqueous solution of NaCl at different temperatures at different molality and at frequency 6 MHz. II. EXPERIMENTAL METHODS Fresh distilled water has been used as solvent for preparing sodium chloride (NaCl) solutions of different concentrations. Sodium chloride used as solute for the solution is of analytical reagent (AR) grade, obtained from E-Merk Ltd (India). The density, viscosity, and ultrasonic velocity were measured as a function of concentration of NaCl at K, K and K. Ultrasonic velocity measurements were made using an ultrasonic interferometer (Model M- 84, supplied by M/S Mittal Enterprises, New Delhi) with the accuracy of ±0.1m s 1. An electronically operated digital constant temperature bath (Model SSI-03 Spl, supplied by M/S Mittal Enterprises, New Delhi), operating in the temperature range of 10 C to 85 C with an accuracy of ±0.1 C has been used to circulate water through the outer jacket of the double-walled measuring cell containing the experimental liquid. The densities of the mixture were measured using a 10-ml specific gravity bottle by relative measurement method with an accuracy of ±0.01 kg m 3. An Oswald viscometer (10 ml) with an accuracy of ±0.001 Ns m 2 was used for the viscosity measurement. The flow time was determined using a digital racer stopwatch with an accuracy of ±0.1s. III. THEORY The following thermodynamic parameters were calculated: 1.1 Rao s constant (R): Rao s constant is also known as molar sound velocity and it is an additive property. It has been found to be invariant with temperature and pressure for un-associated organic and inorganic liquid. R can be evaluated by an equation given by Bagchi et al. ( ). rights Reserved Page 12

2 1.2. Wada s constant: Molar compressibility is also known as Wada s constant, which is dependent on adiabatic compressibility and density, is given by ( ). (2) 1.3. Surface tension: Surface tension can be calculated by using the relation. (3) 1.4. Solvation number: Solvation number is determined by using the formula ( ) ( ). (4) Where M and Mo are molecular weight of Solvent and Solution respectively, and are adiabatic compressibility of Solvent and Solution respectively and x is the number of grams of salt in 100g of the solution. IV. RESULT AND DISCUSSION The experimental values of density, viscosity, ultrasonic velocity and electrical conductivity are presented in Table 1 &2. The calculated values of Rao's constant, Wada's constant, solvation number and surface tension are represented in Table-3 & 4. It is observed from table-2 that, at a particular temperature, velocity increases with increase in concentrations of NaCl and also increases when temperature increases at a particular concentration. With increase in concentration of NaCl, the H-bonded structure of water [11] is disrupted. Electrolytes occupy the interstitial spaces and tend to break the original ordered structure of water. Interaction between solute and solvent molecules results in decrease in free length and increase in density, viscosity and velocity. At a fixed concentration, as temperature increases there is decrease in intermolecular force due to increase in thermal energy of the system which results in decrease in density and viscosity. However, relatively small ions (Na + ) induce higher order in water structure. More the hydration means lower is the compressibility and increase in velocity. Vander Waals and hydrogen bonding interactions are believed to govern the viscosity of Room Temperature Ionic Liquid [12]. Temperature remaining constant, conductivity increases as concentration of NaCl increases. The increase in conductivity depends on the solvent added and the extent to which the ions are dissociated. Electrical conductivity however decreases as temperature increases for a particular concentration of NaCl as shown in igure 1. Conductivity of ionic liquids increases due to the presence of water-rich regions. As temperature increases water evaporates and thus the conductivity decreases. Rao s constant and Wada s constant increases with increase in concentration of NaCl, which indicates the availability of more number of solute molecules in a given region, giving rise to the strong solute-solvent interaction. However, for any concentration both the constants increase slowly with temperature. As temperature increases the molecules are separated due to thermal energy, but the electrostatic interaction between the hydrated sodium ions and the water molecules increase slowly. Surface tension increases rapidly as concentration of NaCl increases but increases slowly when temperature increases at a particular concentration. At higher concentration there is strong molecular attraction between adjacent molecules. As temperature increases the weak electrostatic interaction does not affect the surface tension appreciably. Figure 2, Figure 3 and Figure 4 indicates the change in Rao s constant, Wada s constant and surface tension for various concentrations and temperatures. Solvation number is an important parameter to study the interaction between the solute and solvent. Negative value of solvation number emphasize that the solution is more compressible than the solvent. Zero value of solvation number indicates that, no change occurs in the compressibility of solvent when the solution is formed. Positive solvation number of solution, suggest that, compressibility of the solution at high temperatures and all molalities will be less than that of the solvent. Available Online at : Page 13

3 W ---> S ---> ELECTRICAL CONDUCTIVITY ----> R ---> Volume: 03 Issue: 02 February 2018 (IJRIER) In the present case, solvation number is always negative that means ions and water molecules are more separated than solvent molecules. Negativity decreases rapidly with increase of concentration and slowly with increase of temperature. At low concentration interaction between the solute and solvent is weak; hence the solution is more compressible. At high concentration, the Na + ions form a core component structure through electrostatic bonding with o - in the hydrogen molecule. Due to this, the solvation number decreases. As temperature increases, at any particular concentration negative solvation number decreases slightly. This indicates that the core compact structure become less compact due to the increase in thermal energy of the system. V. FIGURES AND TABLES 160 ~ C O N C E N T R A T I O N O F N A C L 140 R ~ Concentration of NaCl CON. OF NACL------> Figure-1: Electrical conductivity vs Conc. Of NaCl Figure-2: Rao s constant vs Conc. Of NaCl W ~ Concentration of NaCl Concentration of NaCl ---> Figure-3: Wada s constant vs Conc. Of NaCl Figure-4: Surface tension vs Conc. Of NaCl TABLE-1: Experimental values of density and viscosity Concentration of NaCl ---> S ~ Conc. of Nacl Conc. of Nacl ----> Sol. No. Density (ρ)/kg.m -3 Viscosity ( ) x 10-3 /Nsm -2 S S S S S Available Online at : Page 14

4 TABLE-2: Experimental values of ultrasonic velocity and electrical conductivity Sol. No. Ultrasonic velocity(u)/m. s -1 Electrical conductivity ( )/S.m -1 S S S S S TABLE-3: Calculated values of Rao s constant and Wada s constant. Rao's constant(r)/m 3.mol -1 Wada's constant(w)/m 3.mol -1 Sol. No. S S S S S TABLE-4: Calculated values of surface tension and solvation number. Surface tension(s)/n.m -1 Solvation number Sol. No. S S S S S VI. CONCLUSION The result of the present study reveals that the ultrasonic velocity and derived acoustic parameters depend on composition of the solution, indicting the presence of molecular interaction between the component molecules. VI. ACKNOWLEDGEMENTS We are thankful to Management of Ajay Binay Institute of Technology, CDA, sector-1, Cuttack, Odisha, for providing the laboratory for the improvement of research activities in the Institute. REFERENCES [1] Stopniak, I. and Andzejewska, E Highly conductive ionic liquid based ternary polymer electrolytes obtained by in situ photopolymerisation, Elecrochemica Acta., 54: [2] Praharaj, M Ultrasonic and conductometric studies of aqueous potassium chloride solutions at different temperatures, Int.J.Curr.Res.Aca.Rev., 5(6): 1-5. [3] Shelden, R Catalytic reactions in ionic liquids, Chem. Comm., 23: [4] Earle, MJ. and Kenneth, R Ionic liquids. Green solvents for the future, Pure Appl. Chem., 72: [5] Freemantle, M Ionic liquids may boost clean technology development, Chem. Eng. News, 76(13): [6] Brennecke, JF. and Maginn, EJ Ionic liquids: Inovative fluids for chemical processing, AIChE.J, 47: Available Online at : Page 15

5 2389. [7] Cole-Hamilton, DJ Homogeneous catalysis--new approaches to catalyst separation, recovery, and recycling. Science, 299: [8] Bluhrn, ME. Bradley, MG. and Butterick, R Amineborane-based chemical hydrogen storage: Enhanced Ammonia borane dehydrogenation in ionic liquids, J. Am. Chem Soc., 128: [9] Lagrost, C. Carrie, D. and Vaultier, M Reactivities of Some Electrogenerated Organic Cation Radicals in Room-Temperature Ionic Liquids: Toward an Alternative to Volatile Organic Solvents. J. Phys. Chem. A, 107(5): [10] Bates, ED. and Rebecca, D CO 2 Capture by a Task-Specific Ionic Liquid, J. Am. Chem Soc., 124(6): [11] Praharaj, MK. Satapathy, A. Mishra, PR. and Misra, S Study of Acoustical and Thermodynamic Properties of Aqueous Solution of NaCl at different Concentrations and Temperatures through Ultrasonic Technique, Arc of App Sc Res., 4 (2): [12] Bonhote, P. Das, AP and Papageorgiou. N Hydrophobic, Highly conductivity Ambient-Temperature Molten Salts, Inorganic chem., 35(5): About the Authors Dr. Manoj Kumar praharaj was born in a small village named Solar at Cuttack district of Odisha, india. He completed his primery and secondary education at same native place. He completed B.Sc(physics-Hons), M.Sc (Electronics-Spl.), M.Phil (Physics) from Ravenshaw Autonomous college under Utkal University, Odisha. He completed Ph.D (Physics, Ultrasonics) from Ravenshaw University, Odisha. Presently he is working as Assistant Professor in the department of Physics, Ajay Binay institute of Technology, Cuttack, Odisha with 19 years of teaching and 08 years of research experience. He is continuing his research work in experimental and theoretical ultrasonic with 32 numbers of research papers published in journals of national and international repute. Available Online at : Page 16