Naslov
Investigation of the Complex Forming Reactions of Cd2+ and Cl- Ions in 2-Butanone + Water Mixtures by Direct Potentiometry

Autori
Tomaš, Renato ; Tominić, Ivo ; Sokol, Vesna ; Višić ; Marija

Izvornik
Croatica chemica acta (0011-1643) 77 (2004), 3; 519-527

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
2-butanone + water mixtures; chlorocadmium complexes; direct potentiometry; stability constants; thermodynamic quantities

Sažetak
The complex forming reactions of cadmium and chloride ions in 2-butanone + water mixtures (with mass fraction of the organic component 0.05, 0.10 and 0.15) at three ionic strengths and three temperatures were investigated by the method of direct potentiometry by means of calibration straight lines. As that experimental technique has not yet been tested in mixed solvents, first, measurements in 10 % (mass fraction) t-butanol at ionic strength of 1 mol dm-3 and temperatures 288.15, 298.15 and 313.15 K were performed and stability constants of chlorocadmium complexes redetermined. Comparing these values with those obtained by measuring the e.m.f. of concentration cell with transference, reproducibility and applicability of direct potentiometry in that mixed solvent were proven. According to statistical parameters, direct potentiometry retains the precision of the potentiometry of the concentration cell with transference, but, due to the absence of junction potential, it is undoubtedly more accurate. In the mixtures of water and 2-butanone, CdCl+, CdCl2 and CdCl3- complexes were found as well as their concentration stability constants by the method of orthogonal polynomials for each ionic strength and temperature. By the extrapolation of semiempirical straight lines to zero ionic strength, thermodynamic stability constants were obtained. It was found that the Ko values increase with the increase of temperature and with the decrease of relative permittivity of the solvent. From the temperature dependence of Ko, thermodynamic quantities for the complex forming reactions were calculated ; all the reactions are spontaneous, endothermic and lead to an increase in entropy.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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