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UBC Theses and Dissertations

The rate of reaction between bromoacetate and thiosulphate ions in dodium chloride and sea water media Dodimead, Allan John


Rate measurements of the thiosulphate-bromoacetate reaction have been made in sodium chloride and sea water media at 15.3°, 25.2° and 32.0°C and in magnesium chloride at 15.3°C, Rates are more simply dependent on the concentration and kind of cations in the media than upon the ionic strength. The rate constants are approximately 6% higher in neutral solutions of sea water than in sodium chloride media and the higher rate constants are attributed to the presence in sea water of the cations, K⁺, Ca⁺⁺ and Mg⁺⁺. The energy of activation is 16,000±100 cal./mole and the entropy of activation is-6.6 e.u. for the reaction done in both media. The convergence of the rate curves in magnesium and sodium chloride media at high concentrations may be explained by the presence of undissociated species. The magnitude of the correction to the observed rate depends upon the concentration of the cations and the formation constant for the undissociated species. This explanation has been used to account for the decrease in rate in sea water that has been made alkaline.

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