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Complexation of Cd2+ and Cl– Ions in Aqueous Mixtures of 2-Butanol

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Naslov Complexation of Cd2+ and Cl– Ions in Aqueous Mixtures of 2-Butanol
Kompleksiranje Cd2+ i Cl– iona u smjesama vode i 2-butanola
 
Autor Tomaš, Renato
Tominić, Ivo
Višić, Marija
Sokol, Vesna
 
Tema 2-butanol + water mixtures; chlorocadmium complexes; direct potentiometry; stability constants; thermodynamic quantities
 
Opis Reactions of chlorocadmium complex formation have been studied in mixtures of 2-butanol + water (w2-BuOH = 0.05, 0.10, and 0.15) at three ionic strengths and three temperatures by means of direct potentiometry. First, calibration diagrams for cadmium and chloride ions were made, based on e.m.f. (electromotive force) measurements in solution with known concentrations of these ions, followed by e.m.f. measurements in a series of solutions with known concentrations of total cadmium and total chlorides in which complexation took place. Using the latter e.m.f. data and the respective calibration diagrams, concentrations of free cadmium and chloride ions were determined for each ionic strength and temperature. Three complexes were found in each mixed solvent: CdCl+, CdCl2 and CdCl3- . Their concentration stability constants (Kn ' ) were calculated by the method of orthogonal polynomials for each ionic strength and temperature. The thermodynamic stability constants (Kn o) were determined for each temperature in a particular
mixed solvent, and were found to increase with increasing temperature, as well as with decreasing relative permittivity of the mixed solvent, for each complex species. By comparison with the Kn
o constants in the 2-butanone + water solvent, the influence of the organic component was established. Thermodynamic quantities for the complex formation reactions, calculated from Kn o, have shown that complexation is spontaneous, endothermic, and accompanied
by an entropy increase.
Ispitivane su reakcije nastajanja klorokadmijevih kompleksa u smjesama 2-butanol + voda (w2-BuOH = 0,05, 0,10 i 0,15) pri tri ionske jakosti i tri temperature primjenom izravne potenciometrije. Najprije su na temelju EMS mjerenja otopina poznatih koncentracija kadmijevih, odnosno kloridnih iona, izrađeni ba`darni dijagrami za te ione. Zatim su EMS mjerenja izvedena u nizu otopina poznate koncentracije ukupnoga kadmija i ukupnih klorida u kojima dolazi do kompleksiranja. Na temelju tih mjerenja i ba`darnih pravaca, za svaku ionsku jakost i temperaturu, određene su koncentracije slobodnih kadmijevih i kloridnih iona. Za svaku ionsku jakost i temperaturu u pojedinome miješanome otapalu za nađene komplekse CdCl+, CdCl2 i CdCl3- , izračunane su koncentracijske konstante stabilnosti (Kn ' ) primjenom metode ortogonalnih polinoma. Za svaku temperaturu u pojedinome miješanome otapalu određene su termodinamičke konstante stabilnosti (Kn o) koje se, za svaku kompleksnu vrstu, povećavaju porastom temperature kao i sa smanjenjem relativne permitivnosti miješanoga otapala. Usporedbom s konstantama Kn o u otapalu 2-butanon + voda utvrđen je utjecaj organske komponente. Termodinamič ke veličine za reakcije nastajanja kompleksa, izračunane iz Kn o, pokazale su da je kompleksiranje spontano, endotermno te da je praćeno porastom entropije
 
Izdavač Croatian Chemical Society
 
Datum 2005-06-15
 
Vrsta resursa text
 
Format (na primjer PDF) pdf
 
Identifikator http://hrcak.srce.hr/24
http://hrcak.srce.hr/file/24
 
Izvor Croatica Chemica Acta (cca@chem.pmf.hr); Vol.78 No.2; ISSN 0011-1643 (Print); ISSN 1334-417X (Online)
 
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