Viscosities of solutions of electrolytes and nonelectrolytes inN-methylacetamide at 35° and 55°C |
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Authors: | Peter T. Thompson Marciana Durbano Joseph L. Turner Robert H. Wood |
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Affiliation: | (1) Department of Chemistry, Swarthmore College, 19081 Swarthmore, Pennsylvania;(2) Department of Chemistry, University of Delaware, 19711 Newark, DE |
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Abstract: | The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, and tetrabutylammonium tetrabutylborate, as well as several nonelectrolytes have been measured in the high dielectric constant solvent N-methylacetamide (NMA) at 35 and 55°C. The relative viscosities were fitted to the extended Jones-Dole equation, = 1 + AC1/2 + BC + DC2. The pattern of behavior of the B coefficients is roughly similar to that observed in H2O. However, the small ions have exceptionally large B values in this solvent due to strong solvation effects, while the large organic ions do not display the sharp crossing of the Einstein law, B=2.5 V, characteristic in H2O of hydrophobic interaction. The D coefficients roughly parallel the B behavior and display remarkably regular ionic trends. This suggests that they arise largely from hydrodynamic origins. Nonelectrolytes have small or negative B coefficients showing that the Einstein law is not applicable at the molecular level and that nonelectrolytes are poor models for structurally similar ions. A simple mixture law is presented as an alternative to the Einstein law to explain the B coefficients. |
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Keywords: | Viscosity electrolyte, nonelectrolyte alkali metal halide tetraalkylammonium ions solvation jones and Dole equation nonaqueous solvent N-methylacetamide |
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