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Meritve gostot raztopin kot preizkus teorije o ujemanju afinitet ionov do vode
Stupar, Anita (Author), Cerar, Janez (Mentor) More about this mentor... This link opens in a new window

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Abstract
V diplomski nalogi smo merili gostote vodnih raztopin različnih alkalijskih halidov in njihovih binarnih mešanic z namenom, da preučimo volumske spremembe pri mešanju teh raztopin. Merili smo mešanice dveh raztopin različnih soli enakih koncentracij, pri tem pa smo spreminjali tako koncentracijo teh elektrolitov kakor tudi medsebojna volumska razmerja, v katerih smo mešali ti raztopini. S temi meritvami smo želeli preveriti, ali je z natančnim merjenjem gostot možno potrditi teorijo o ujemanju afinitet ionov do vode. Predpriprava merjenih raztopin je zajemala natančno pripravljanje raztopin s tehtanjem in preverjanje koncentracij s potenciometrično titracijo. Gostote vseh raztopin in njihovih mešanic smo merili pri 25 °C s pomočjo gostotomera na nihajočo U-cevko. Dobljene meritve so nihajni časi, iz katerih smo na podlagi predhodno umerjenega gostotomera izračunali gostote. Iz gostot smo izračunali realne volumne raztopin in jih primerjali z volumni, ki bi jih imele te raztopine, če bi se vedle idealno. Odstopanja od idealnega obnašanja raztopin smo predstavili v grafih kot funkcijo volumskega razmerja mešanja in koncentracije. Pri mešanju raztopin dveh elektrolitov, ki sta vsebovala skupni ion, so bile volumske spremembe tako majhne, da so bile te spremembe velikostnega reda eksperimentalnih napak. Največje volumske spremembe smo opazili pri mešanju raztopin NaBr in KF višjih koncentracij (največjo volumsko spremembo ravno pri najvišji, to je 4 M raztopini). Zaradi precej podobnih ionskih radijev natrijevega in kalijevega iona je pri tem mešanju opažene volumske spremembe težko pripisati veljavnosti teorije o ujemanju afinitet ionov do vode. So pa te volumske razlike lahko tudi posledica eksperimentalnih napak zaradi interakcije fluoridnih ionov s stekleno oscilirajočo cevko.

Language:Slovenian
Keywords:volumske spremembe, idealne raztopine, gostotomer na nihajočo U-cevko, gostota
Work type:Bachelor thesis/paper (mb11)
Tipology:2.11 - Undergraduate Thesis
Organization:FKKT - Faculty of Chemistry and Chemical Technology
Year:2019
COBISS.SI-ID:1538478531 Link is opened in a new window
Views:154
Downloads:55
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Secondary language

Language:English
Title:Solution density measurements as a test of the law of matching water affinities
Abstract:
In this diploma thesis we measured the density of solutions of different alkali halides and their binary mixturesto examine the volume changes that occur when the solutions are mixed. The mixing of chosen two solutions of diferent salts was carried out with solutions of the same concentration as a function both of the concentration and of the volume ratios between the both solutions. Using accurately measured densities of these volume changes we wanted to verify if the law of matching water affinities can be confirmed with accurate density measurements. Preparation of the measured solutions consisted of weighing and precise determination of solution concentrations with the use of potentiometric titration. The densities of the solutions were determined with the help of an oscillating U-tube density meter at 25 °C. From the measured oscillating times we calculated the densities of solutions; the density meter was calibrated beforehand. Using these densities we calculated the real volumes of the solutions and compared them to the volumes if the solutions were ideal. Deviations from the ideal behavior of the solutions are presented in graphs as a function of the volume ratio of mixing and concentration. When mixing solutions of two electrolytes containing a common ion, the volume changes were so small that these changes were of the order of magnitude of the experimental errors. The largest volumetric changes were observed in mixing of NaBr and KF solutions of higher concentrations (the largest volumetric change was exactly at the highest, i.e., 4 M solution). Due to the rather similar ionic radii of sodium and potassium ions it is difficult to attribute the validity of the law of matching water affinities from the observed volume change during mixing. Morever, these observed differences may also be due to experimental errors as a result of the interaction of fluoride ions with a glass oscillating tube.

Keywords:volume changes, ideal solutions, density meter with oscillating U-tube, density

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