magistrsko delo
Anja Kramer (Author), Janez Cerar (Mentor), Franc Požgan (Thesis defence commission member), Bojan Šarac (Thesis defence commission member)

Abstract

Zakon o ujemanju afinitet ionov do vode, ki ga je intuitivno postavil K. D. Collins, predpostavlja, da nasprotno nabiti ioni z enakimi ali z zelo podobnimi afinitetami do vode med seboj tvorijo kontaktne ionske pare (CIP), ioni z dovolj različnimi afinitetami do vode pa ionskih parov ne tvorijo. V magistrskem delu sem sledeč Collinsovem zakonu proučevala mešanje različnih raztopin alkalijskih halidov. Osredotočila sem se predvsem na analizo toplotnih efektov nastalih pri izotermnem mešanju vodnih raztopin različnih parov alkalijskih halidov enakih koncentracij, izvedenem na izotermnem titracijskem kalorimetru (ITC). Z namenom, da bi potrdila rezultate meritev z ITC kalorimetrom, sem izmerila še električne prevodnosti ob mešanju vodnih raztopin različnih parov soli in za dva para soli tudi gostote takšnih mešanic raztopin soli. Primarni cilj raziskovanja je bil, da ugotovim, ali pri določenih parih soli (glede na Collinsovo pravilo) prihaja do tvorbe kontaktnih ionskih parov (CIP). Rezultati entalpij mešanja so pokazali, da pri po velikosti enakih (zelo podobnih) ionih ne prihaja do obsežne tvorbe CIP (kar smo potrdili tudi z meritvami električne prevodnosti). Iz izmerjenih toplot mešanja (linearno naraščanje toplot s spreminjanjem sestave mešanice soli in majhni toplotni efekti) sem ugotovila, da pri mešanju večine parov soli med seboj ne prihaja do kakršnih koli drugih nepričakovanih procesov. Izjeme so bile pri dodajanju raztopine CsF (in tudi LiF) v raztopino druge soli, kjer na grafu odvisnosti integralne toplote mešanja ΔHint. od deleža dane soli v mešanici raztopin dveh soli (X(MX)) vidimo, da se vrednost ΔHint. na dveh ali treh delih vsake krivulje ustali. Razlog za dano sosledje endotermnih toplotnih efektov je vsaj delno posledica hidrolize fluoridnega iona in interakcije fluoridih ionov s steno titracijske celice. Meritve entalpij mešanja so tudi pokazale, da so entalpije mešanja danega para soli tem večje, čim višja je začetna koncentracija obeh raztopin soli.

Keywords

alkalijski halidi;entalpije mešanja;izotermna titracijska kalorimetrija;zakon o ujemanju afinitet ionov do vode;Collinsova pravila;električna prevodnost;Debye-Hücklova teorija;Hofmeistrova vrsta;magistrska dela;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher: [A. Kramer]
UDC: 544.332(043.2)
COBISS: 1538440131 Link will open in a new window
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Downloads: 194
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Other data

Secondary language: English
Secondary title: Enthalpies of mixing of aqueous solutions of alkali halides as a test of the Law of Matching Water Affinities
Secondary abstract: Law of matching water affinities is intuitive law postulated by K. D. Collins. This law assumes that pairs of ions of the opposite charge with identical or very similar water affinity form contact ion pairs (CIPs) while no ion pairs are formed between ions with different water affinity. In the present master thesis, due to the Collins law, mixing of aqueous alkali halides solutions has been examined. The main focus was on analyses of heat effects, which arise by the isothermal mixing of different pairs of aqueous alkali halides solutions of the same concentration, determined by isothermal titration calorimetry (ITC). In order to validate the results measured on ITC, we also measured the electrical conductivity and density of such aqueous alkali halide mixtures. Primary objective of the research was to discover, if formation of contact ion pairs occur when certain pairs of salts (according to Collins’ law) are mixed. The measured values of the enthalpy of mixing ions of the same (very similar) sizes do not indicate extensive formation of CIPs. This was confirmed by electrical conductivity measurements. From the measured heats of mixing, I have found due to low thermal effects and linear increase (decrease) of heat by changing the composition of the salt mixture that when mixing most of the salt pairs there are no other unexpected processes. Exceptions were made when adding a solution of CsF (and also LiF) to the solutions of second salt, where is in the graph ΔHint. (X(MX)) the value of ΔHint. on two or three parts of each curve settle down. The reason for the given function of thermal effects is at least in part due to the hydrolysis of the fluoride ion and possibly also due to the interaction of fluoride ions with the wall of titration cell. Measurements of the enthalpy of mixing has also showed that the enthalpy of mixing for a given salt pair is increasing with initial concentration of involved aqueous salt solutions.
Secondary keywords: alkali metal halides;heats of mixing;isothermal titration calorimetry;law of matching water affinities;electrical conductivity;
Type (COBISS): Master's thesis/paper
Study programme: 1000375
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, smer Kemija
Pages: 61 str.
ID: 11236304