The kinetics of the electron transfer reaction U(IV) + T1(III) → U(VI) + T1(I) were examined in aqueous perchloric acid solution. The rate law was found to be of the form [ Formula omitted ] The two rate constants were identified with reaction paths involving activated complexes of the compositions (U.OH.T1)⁶⁺ and (U.O.T1)⁵⁺ , respectively. The corresponding heats and entropies of activation, evaluated from rate measurements over the temperature range 16 to 25°, are ΔH₁± = 24.6 kcal/mole, ΔH₂± = 21.7 kcal/mole, ΔS₁±= 16 e.u. and ΔS₂±= 7 e.u. The effect of ionic strength and the specific effects of various anions and cations on the rate were examined. The results suggest, but do not prove, that the reaction occurs through a single two-equivalent step rather than through successive one electron changes. The homogeneous oxidation of carbon monoxide by metal ions in aqueous solutions was studied. At temperatures below 80° only Hg²⁺ and MnO₄¯ were found to oxidize carbon monoxide. The ions Cu²⁺ , Ag⁺ , Hg₂²⁺ , Fe³⁺ , T1³⁺ and Cr₂O₇²¯, were inactive. Kinetic measurements of the reaction 2Hg²⁺+ CO + H₂O → Hg₂²⁺+ + CO₂ + 2H⁺ in dilute perchloric acid over the temperature range 26 to 54° yielded the rate law [ Formula omitted ] The activation parameters are ΔH± = 14.6 kcal/mole and ΔS± =-13 e.u. It is believed that the reaction proceeds by a mechanism which involves the insertion of CO between Hg²⁺ and a coordinated water molecule [ Formula omitted ] The oxidation of carbon monoxide by MnO₄¯ was found to proceed readily over the temperature range 28 to 50°. The rate law was found to be [ Formula omitted ] with ΔH± = 13 kcal/mole and ΔS± = -17 e.u., both substantially constant over the pH range 1 to 13. The rate determining step is considered to be the formation of hypomanganate MnO₄¯+ CO + H₂O → MnO₄³¯ + CO₂ + 2H which then undergoes further fast reactions to yield MnO₄²¯ in basic solution and MnO₂ in acid and neutral solutions. A remarkable feature of the latter reaction is its very marked sensitivity to catalysis by Ag⁺ and Hg²⁺ (but not by Cu²⁺, Cd²⁺, Fe³⁺, or T1³⁺ ). The rate law of the catalyzed path is, in each case, [ Formula omitted ] where M = Ag⁺ or Hg²⁺. For Ag⁺, k at 0° is 1.10 x 10⁵ M¯² sec¯¹ with ΔH± = 1.3 kcal/mole and ΔS± = -30 e.u. For Hg²⁺, k at 0° is 1.09 x 10³ M¯² sec¯¹ with ΔH± = 6.5 kcal/mole and ΔS± = -21 e.u. It is suggested that the remarkably high reactivities exhibited by carbon monoxide in these catalytic reactions are related to favourable oxidation paths involving intermediates such as [ Formula omitted ] / Science, Faculty of / Chemistry, Department of / Graduate

The experimental work described in this thesis is designed to give information on the thermodynamic properties and chemical reactivity of the surface of an ionic crystal. The principal studies concern halogen exchange between hydrogen chloride gas and the surface of sodium bromide. For this reaction, like any ordinary chemical reaction, both kinetics and equilibrium may be investigated. In the present study, the most Interesting feature has been the measurement of the equilibrium constant and the calculation therefrom of the changes in thermodynamic properties attending the replacement of a bromide ion by a chloride ion in the surface. This appears to be the first reported measurement of an equilibrium constant involving concentrations in a solid surface. The work differs sharply from previous studies of isotopic exchange, which have been exclusively kinetic. The equilibrium is best represented by the equation [formula omitted] where X and (1-X) are the fractions of the surface anion sites occupied by Cl⁻ and Br⁻ respectively, ∆°S refers to the entropy changes of the exchanged ions at X = 0, and Si(X) describes the effect of any anion on the entropy of its neighbours in the surface. The equation indicates the formation of a two-dimensional solid solution of NaCl and NaBr, deviating from ideality through the term Si(X), so that the equilibrium constant K is a function of X. Since K is independent of temperature (20°-95°C.), ∆H = 0 and the equilibrium equation contains entropy terms only. From the value K = 6X10⁻³ at X = 0 it is estimated that [formula omitted] where S°Cl⁻ and S°Br⁻ refer to surface ions. The variation of K with X is used to arrive at a tentative estimate, based on some simplifying assumptions, of [formulas omitted]. Of this, about -2 cal/mole deg. K may be a simple mass effect. These large decreases in entropy are discussed in relation to the probable structure of the surface of sodium bromide; they are consistent with the "Verwey distortion" in which the anions are displaced outwards from the ideal surface, the distortion increasing, ceteris paribus, with the size and polarizability of the anions. The kinetics of the exchange reaction have been studied. It has not proved possible to analyze the rate curves in detail. The most striking feature, in comparison with previous studies, is that all reactions involving bromine (initially in either the gaseous or the solid phase) are faster than those involving chlorine isotopes only. The reason for this may be either the availability of d-orbitals of bromine for bonding in a transition complex, or the polarizability of the bromine atom. The exchange reaction has been used to study diffusion of chloride ions into sodium bromide at room temperature. It is possible to measure diffusion coefficients of about 10⁻²²cm²sec⁻¹, smaller by a factor of about 10⁵ than can be measured by most conventional methods. The results suggest that diffusion takes place principally along dislocations. The dehydration of high surface area sodium bromide has been studied, and is found to take place at a vapour pressure different from the equilibrium value for the system, NaBr.2H₂0; NaBr; H₂O. This is attributed to the formation of a "surface hydrate" overlying the lattice of anhydrous NaBr. This process may be regarded as adsorption with a discontinuous isotherm, and implies that the NaBr surface is energetically homogeneous. It has been found that color centers may readily be produced in the alkali halides by a Tesla Coil discharge. Centers thus produced in sodium chloride have been examined spetroscopically. The technique may be useful in experiments to establish the mechanism of exchange reactions such as that described in this thesis. / Science, Faculty of / Chemistry, Department of / Graduate

The physical and inorganic chemistry of solutions in difluorophosphoric acid, HPO₂F₂, has been studied, as part of a general study of solutions in non-aqueous protonic solvents. Difluorophosphoric acid is a colourless, associated liquid which might be expected to have solvent properties similar to those of other protonic systems such as H₂O, H₂SO₄ and HSO₃F. However, electrical conductivity studies of solutions of various electrolytes and nuclear magnetic resonance studies of solutions of alkali metal difluorophosphates indicate that the acid is a poor solvent for electrolytes and that ion-pairing is probably extensive. Acid-base behaviour in HPO₂F₂ has been extensively investigated. Compounds which behave as bases in this system include metal difluorophosphates, chlorides, nitrates and carbonates, organic amines, and some organic nitro-compounds and carboxylic acids. Inorganic molecules such as H₂SO₄, HSO₃F and SbF₅ behave as acids. Reaction between an acid and a base in HPO₂F₂ commonly result in the formation of an insoluble salt. The reaction between KPO₂F₂ and SbF₅, for example, has been used to prepare the new compound KSbF₅PO₂F₂. To further investigate the factors affecting acid strengths, cryoscopic and electrical conductivity studies of various inorganic oxy-acids were carried out in nitrobenzene, as solvent. The acids H₂SO₄, HSO₃F and HPO₂F₂ appeared to be virtual non-electrolytes in nitrobenzene, with H₂SO₄ apparently exhibiting some polymerization. / Science, Faculty of / Chemistry, Department of / Graduate

Calorimetrically determined ΔH° values are given for the stepwise formation of chelate species between serinate ion and the divalent metal ions of Co, Ni, Cu, Zn, and Cd. These values of ΔH° are compared with those reported in the literature and were combined with values of ΔG° (log K) found in the literature to calculate values of ΔS°. These values of ΔG° and ΔS° are listed also. A new method of standardizing dilute ferrous ion solutions is reported. This procedure makes use of the thermometric titration technique to detect the equivalence point for the reaction of K_2Cr_2O_7 with ferrous ion. A method is described which makes use of dilute ferrous ion solutions to determine the concentration of 2,2'-bipyridine in aqueous solution. It was found that the 2,2'-bipyridine concentration decreases with time.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1965 I72 / Master of Science

The solubility of diuron was determined in binary and ternary cosolvent-water systems. The binary systems were composed of a completely miscible organic solvent (CMOS) and water while the ternary systems incorporate partially miscible organic solvents (PMOS) into the binary systems. Due to the low aqueous solubilities of trichloroethylene and toluene, the PMOS's do not behave as cosolvents and they do not play an important role in altering solubility.

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