Electrochemical studies of nonaqueous solutions.
Item
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Title
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Electrochemical studies of nonaqueous solutions.
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Identifier
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AAI9304681
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identifier
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9304681
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Creator
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Kahanda, Chandrakanthi.
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Contributor
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Adviser: Orest Popovych
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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The liquid-junction potential, E{dollar}\sb{lcub}\rm j{rcub}{dollar}, in cells with junctions between two solvents is attributed to the transport of solvated ions across the solvent-solvent interface. The E{dollar}\sb{lcub}\rm j{rcub}{dollar} is formally divided into E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} and E{dollar}\sb{lcub}\rm j,s{rcub}{dollar} components, which account, respectively, for the transport of the ions and the solvent molecules across the interface. The E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} values between electrolyte solutions in water and methanol-water (MeOH/H{dollar}\sb2{dollar}O), ethanol-water (EtOH/H{dollar}\sb2{dollar}O), acetonitrile-water (AN/H{dollar}\sb2{dollar}O), dimethylformamide-water (DMF/H{dollar}\sb2{dollar}O) and dimethylsulfoxide-water (DMSO/H{dollar}\sb2{dollar}O) solvent systems were calculated using both the old equation from the literature and a new formulation developed in our laboratory by Anna Berne (4). The new formulation for E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} accounts for the variation of the transport numbers and the chemical potentials of the ions crossing the boundary with the solvent composition across the diffusion layer.;Conductance measurements were carried out in methanol-water mixtures to obtain the limiting equivalent conductance of sodium chloride. Using these data and available literature values, the limiting transport numbers of sodium, chloride and hydrogen ions were calculated for NaCl and HCl solutions over the entire range of methanol-water solvents.;Transfer activity coefficients for the nitrate ion in acetonitrile-water mixtures, required for the E{dollar}\sb{lcub}\rm j{rcub}{dollar} calculation, were determined by using the solubility method and from the e.m.f. of cells with liquid junction.;Comparison of the E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} calculations from both the old equation and the new equation were carried out for the above systems. For HCl in MeOH-water, EtOH-water, DMF-water and DMSO-water and for AgNO{dollar}\sb3{dollar} in AN-water solvent systems, large differences in the E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} values between the old and the new equations were observed because of the transport numbers and transfer activity coefficients of ions go through a very pronounced minimum or a maximum. The difference in E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} values were appreciable for the solvent compositions where a maximum or a minimum was observed for the transfer activity coefficients or transport numbers.;E{dollar}\sb{lcub}\rm j,s{rcub}{dollar} has been described in general terms as that component of E{dollar}\sb{lcub}\rm j{rcub}{dollar} which is determined by the passage of solvent molecules rather than ions, across the junction. The term E{dollar}\sb{lcub}\rm j,s{rcub}{dollar} depends on the two solvents forming the junction, but there is no formula from which it can be calculated. Here, the E{dollar}\sb{lcub}\rm j,s{rcub}{dollar} was estimated from the experimental e.m.f.'s of cells with liquid junction between pairs of solutions mentioned above and the calculated E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar}. The E{dollar}\sb{lcub}\rm j,s{rcub}{dollar} values were higher than the E{dollar}\sb{lcub}\rm j,ion{rcub}{dollar} values for the dipolar aprotic systems, whereas the reverse was true for the protic systems.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
