Issue 7, 1995

Temperature coefficients of Ag/Ag+ and Ag/Ag+–cryptand 222 electrode potentials, thermodynamics of Ag+–cryptand 222 complex formation and molar transfer properties for Ag+ cations into aprotic media

Abstract

Temperature coefficients of the stability constants, d log K(Ag+222)/dT, of Ag+ complexes with cryptand 222, Ag+222 cryptate (Ag+222) have been derived from potentiometric titrations at different temperatures in acetone (Ac), acetonitrile (AN), propanenitrile (PN), butanenitrile (BuN), benzonitrile (BN), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO), propylene carbonate (PC) and tetramethylene sulfone (sulfolane, TMS). The temperature coefficients of the standard electrode potentials, dE0/dT, for the Ag/Ag+ and Ag/Ag+222 couples have been derived from potentiometric measurements in a non-isothermal cell, where the reference electrode was kept at a constant temperature of 25 °C. It has been found that while the dE0/dT value for the Ag/Ag+ couple depends strongly upon the solvent, the corresponding temperature coefficient for the Ag/Ag+222 cryptate electrode is similar in all the solvents studied and can be approximated as dE0(Ag/Ag+222)/dT= 0.69 mV K–1 with a standard error of 0.03 mV K–1. Single-ion entropies of the Ag+ cation transfer from acetonitrile have been derived both from dE0(Ag/Ag+)/dT, applying the assumption of negligible thermal diffusion potential between cold and hot parts of the non-isothermal cell as well as from d log K(Ag+222)/dT, applying the ‘cryptate extrathermodynamic assumption’. Gibbs energies, enthalpies and entropies of silver(I) complexation by cryptand 222 agree well with literature data obtained employing different techniques.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1995,91, 1097-1101

Temperature coefficients of Ag/Ag+ and Ag/Ag+–cryptand 222 electrode potentials, thermodynamics of Ag+–cryptand 222 complex formation and molar transfer properties for Ag+ cations into aprotic media

A. Lewandowski, A. Szukalska and M. Galiński, J. Chem. Soc., Faraday Trans., 1995, 91, 1097 DOI: 10.1039/FT9959101097

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