diplomsko delo
Metka Vidic (Author), Aljana Petek (Mentor), Darinka Brodnjak-Vončina (Co-mentor)

Abstract

Diplomsko delo temelji na eksperimentalnem delu. Izvedli smo eksperiment oksidacije askorbinske kisline s heksacianoferatnim(III) ionom. Ugotavljali smo vpliv ionske moči na hitrost kemijske reakcije. Eksperimentalno delo je potekalo od marca do maja 2012 na Fakulteti za kemijo in kemijsko tehnologijo Univerze v Mariboru, in sicer v laboratoriju za fizikalno kemijo in v laboratoriju za analizno kemijo. Potek kemijske reakcije smo spremljali s spektrofotometričnimi meritvami. Pri valovni dolžini 419 nm smo merili spreminjanje absorbance heksacianoferatnega(III) iona. Ker smo želeli ugotoviti, kako ionska moč vpliva na potek izbrane kemijske reakcije, smo reakcijo izvedli v raztopinah z različnimi koncentracijami natrijevega nitrata ter pri konstantnem pH-ju in temperaturi. Meritve smo opravili s pomočjo Cary 1 UV-Vis spektrofotometra. Vsako K3[Fe(CN)6]-NaNO3 raztopino smo posebej zmešali s H2Asc-HNO3-EDTA raztopino v razmerju 1 : 1. Meritve absorbance Fe%(CN)%_6^(3-) smo uporabili za izračun realne vrednosti konstante reakcijske hitrosti pri konstantnem pH-ju in temperaturi ter pri različnih ionskih močeh raztopine. S pomočjo Debye-Hückel zakona smo nato izračunali konstanto reakcijske hitrosti pri neskončni razredčitvi, ki je neodvisna od ionske moči. Ugotovili smo, da povečana ionska moč pospeši hitrost izbrane reakcije. Ugotovili smo, da so večje opazovane konstante reakcijskih hitrosti pri večji ionski moči. Tako smo z eksperimentom pokazali, da v raztopinah z višjo koncentracijo natrijevega nitrata oksidacija askorbinske kisline s heksacianoferatnim(III) ionom poteka hitreje. Vrednost Z1Z2, ki sta naboja ionov, ki sodelujeta v hitrost določujoči stopnji reakcije, smo dobili 3,04, kar je zelo blizu teoretične vrednosti 3.

Keywords

diplomska dela;anorganska kemija;ioni;askorbinska kislina;kinetika;spektrofotometrija;

Data

Language: Slovenian
Year of publishing:
Source: Maribor
Typology: 2.11 - Undergraduate Thesis
Organization: UM FNM - Faculty of Natural Sciences and Mathematics
Publisher: [M. Vidic]
UDC: 546(043.2)
COBISS: 19366664 Link will open in a new window
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Other data

Secondary language: English
Secondary title: ǂThe ǂeffect of ionic strength on the oxidation of ascorbic acid by hexacyanoferrate (III) ion
Secondary abstract: This diploma thesis is based on experimental work. We performed an experiment of oxidation of ascorbic acid by hexacyanoferrate (III) ion. We tried to find out the effect of ionic strength on the rate of the chemical reaction. The experimental work was carried out between the March and the May 2012 at the Laboratory for Physical Chemistry and at the Laboratory for Analytical Chemistry, at the Faculty of Chemistry and Chemical Engineering, University of Maribor. The progress of the chemical reaction was monitored with spectrophotometric measurements. We measured the variation of absorbance at 419 nm wavelength of hexacyanoferrate(III) ion. We carried out the experiments with various concentrations of sodium nitrate, and at constant pH and temperature, because we wanted to find out how the ionic strength influences the progress of the studied chemical reaction. The measurements were performed with the Cary 1 UV-Vis spectrophotometer. Each K3[Fe(CN)6]-NaNO3 solution was separately mixed with H2Asc-HNO3-EDTA solution, in proportion 1:1. The measurements of absorbance of Fe%(CN)%_6^(3-) were used for calculating the real value of reaction rate%s constant at various ionic strengths of the solution, and at a constant pH and temperature. With the help of Debye-Hückel theory we calculated the constant of the reaction rate at infinite dilution, which is independent of ionic strength. We concluded that increased ionic strength accelerates the rate of the studied reaction. We found out that the observed constants of reaction rates are increasing with ionic strength of the medium. This experiment showed that in solutions with higher concentration of sodium nitrate the oxidation of ascorbic acid by hexacyanoferrate(III) ion proceeds faster. The value of Z1Z2 that represent the ions% charges which take part in the rate-determining step of reaction was 3.04, which is very close to the theoretical value of 3.
Secondary keywords: hexacyanoferrate(III) ion;ascorbic acid;ionic strength;chemical kinetics;spectrophotometry;
URN: URN:SI:UM:
Type (COBISS): Undergraduate thesis
Thesis comment: Univ. v Mariboru, Fak. za naravoslovje in matematiko, Oddelek za kemijo
Pages: XIV, 68 f.
Keywords (UDC): mathematics;natural sciences;naravoslovne vede;matematika;chemistry;crystallography;mineralogy;kemija;inorganic chemistry;anorganska kemija;
ID: 994175