engleski

Potentiometry in Mixed Solvent–Electrolyte Systems

This lecture will encompass a part of the investigation of our group as a contribution to studies of the thermodynamic properties of electrolytes in the mixture water + organic solvent. Insight into the properties of the mixed solvent can be got through its influence on the electrokinetic and thermodynamic behaviour of dissolved electrolyte. The measurement of the potential difference (pd) of reversibile galvanic cell over a range of temperature makes it possible to obtain the thermodynamic quantities for the cell reaction, and for the transfer of electrolyte from water to the mixed solvent. The mean activity coefficients of electrolytes may also be calculated from these measurements. Recently in our laboratory the unsymmetrical electrolyte cadmium chloride (CdCl2) was examined potentimetrically using chemical cell without liquid junction: CdHgsat/CdCl2(m) in Z/AgCl(s)/Ag(s), where Z signifies a mixture of water with organic solvent of varied fraction. Using pd-values at different molalities (m) for a given temperature (T) standard molal pd (Eom) can be determined. In water solutions, and even more pronouncedly in media of lower permitivity, CdCl2 forms complexes. Hence, mathematical treatment of the potentiometric data must include stability constants of chlorocadmium complexes. Basic ideas and aims, as well as experimental and computational approach to the title theme, will be presented in detail by this lecture through the following headings: 1. Introduction, 2. Applications of potentiometry, and 3. Thermodynamic study of CdCl2 in mixed solvents.

potentiometry ; electrolytes ; mixed solvents ; thermodynamic quantites

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