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exp2-f conductimetry - CHM171L A11 Physical Chemistry...

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CHM171L / A11 Physical Chemistry Laboratory 2 1 st Quarter S.Y. 2010-2011 Conductimetry: Determination of the Electrical Properties of Solutions Calderon, Edna 1 , Palomaria, Ralph Matthew 2 ,Pineda,Jermaine Marianne 2 , Regulacio, Anna Rafaela 2 1 Professor, CHM171L/A11, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology; 2 Student, CHM171L /A11 , School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology ABSTRACT The experiment is on the topic of conductimetry, specifically the identification of the electrical properties of solutions. Here, the relative mobility of some monovalent ions is to be determined by measuring the conductance of solutions of electrolytes. The specific conductance of an electrolyte solution is a measure of its ability to conduct electricity . Among the reagents used, sodium acetate appeared to have the lowest conductance. The order of decreasing conductance is—NaOH, NaCl, HCl, NH 4 Cl, NaC 2 H 3 O 2 .The second part of the experiment was the determination of the dissociation constant of a weak electrolyte. Dissociation constant measures the propensity of a larger object to dissociate reversibly into smaller components, as when a complex falls apart into its component molecules , or when a salt splits up into its component ions . It can be seen that the resulting concentration versus the conductance plot was a straight line of positive slope. Thus, the graph shows that a two-fold increase in the concentration also means a twofold increase in the conductance of the solution. INTRODUCTION The conductivity (or specific conductance) of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter (S/m).Conductivity measurements are used routinely in many industrial and environmental applications as a fast, inexpensive and reliable way of measuring the ionic content in a solution. For example, the measurement of product conductivity is a typical way to monitor and continuously trend the performance of the water purification systems. In many cases, conductivity is linked directly to the total dissolved solids (T.D.S.). High quality deionized water has a conductivity of about 5.5 μS/m, typical drinking water in the range of 5-50 mS/m, while sea water about 5 S/m (i.e., sea water's conductivity is one million times higher than deionized water). Conductivity is traditionally determined by measuring the AC resistance of the solution between two electrodes. The electrical conductivity of a solution of an electrolyte is measured by determining the resistance of the solution between two flat or cylindrical electrodes separated by a fixed distance. An alternating voltage is used in order to avoid electrolysis. Typical frequencies used are in the range 1-3 kHz. The dependence on the frequency is usually small. The resistance is measured by a conductivity meter. A wide variety of instrumentation is commercially available. There are two types of cell, the classical type with flat or cylindrical
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