Chemistry and Chemical Biology ETDs

Publication Date

12-1972

Abstract

The acidity of hydrofluoric acid in mixed ethanol/ water solvent systems was studied by determining the pKa of HF in a number of different ethanol concentrations. The effect of changing temperature on the acidity of HF in these media was also examined.

The pKa's were determined using a lanthanum fluoride membrane Fluoride Specific Ion Electrode and a glass pH electrode versus the same reference electrode. The method eliminates the need to determine liquid junction potentials. By determining the pKa for HF in each ethanol/water mixture, at a number of different temperatures, thermodynamic parameters, such as free energy, enthalpy, entropy, and heat capacity for the transfer of HF from water to the ethanol/water mixtures could be calculated. The results of these calculations show an increase in free energy for the transfer that is essentially entropy controlled.

The acidity of HF in mixed ethanol/water media was com­pared to the acidity of some carboxylic acids in the same media. Plots of pKa versus ethanol concentration were found to be very similar for all of the acids, leading to the conclusion that changes in acidity in varying ethanol concentrations are more dependent upon solvent effects than upon the molecular structure of the acid.

Estimations of the medium effects activity coefficients for HF and F- were made using published data of medium effects activity coefficients for , , and HC1.

Language

English

Document Type

Thesis

Degree Name

Chemistry

Level of Degree

Masters

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Nicholas Ernest Vanderborgh

Second Committee Member

Robert Edwin Tapscott

Third Committee Member

Edward A. Walters

Fourth Committee Member

Bernard Thomas Kenna

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