Salt effects and oscillating reactions in aqueous systems.
thesisposted on 19.11.2015, 08:46 by Stephen Harvey. Morris
This thesis is concerned with two studies of kinetics in aqueous solutions; (i) salt-effects on kinetics in water, (ii) oscillating reactions. The first-order rate constants for the aquation of tris (5-nitro-1,10-phen) iron (II) in water and in aqueous salt solutions were measured using a Unicam SP 1800 A spectrophotometer. The effects of the added electrolytes on the magnitude of the rate constants are discussed in the light of past work, classical expressions and a treatment involving the effects of added salt on the initial and transition states. The first-order rate constants for the aquation of sulphur trioxide trimethylamine in water and in aqueous salt solutions were also measured, by titrating the acid produced against a solution of sodium hydroxide. The effects of added electrolytes on the magnitude of the rate constants proved strikingly similar to those, observed for the aquation of tris (5-nitro-1,10-phen) iron (II). The results are discussed in the light of this similarity. The change in the redox potential and the bromide ion concentration with time, during the Belousov reaction, one of the few known oscillating reactions, were measured using a platinum electrode and a bromide sensitive electrode respectively. Under specified sets of conditions, the induction period (the period prior to oscillation) and the frequency of oscillation were obtained. Experiments to determine the effects of temperature, added t-butyl alcohol and added sodium dodecyl sulphate, on both the induction period and frequency of oscillation are described. Also described is an experiment to determine the decay of oscillations with time. The results of these experiments are discussed with respect to the mechanism of this reaction. Chemical kinetic models, simulating the oscillatory behaviour of experimentally observed reactions are described. The results of a computer analysis on the Oregonator, a model based on the Belousov reaction, are discussed.