Thiosulfate And Iodine Reaction Lab Report

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In general, this experiment was able to accomplish and establish the rates at which persulfate ions are able to oxidize iodine ions. The reaction between thiosulfate and iodine is known to be rapid, unless there is a sufficient amount of thiosulfate present for the iodine to react with. When thiosulfate is reacting with iodine, the solution will remain colourless, until all the thiosulfate is used up. After a short while, the clear solution will turn into a deep blue when iodine binds to starch. This process allows the rate of reaction to be determined for the persulfate reaction, when the ability to record time is accurate.
The first part of this experiment was to determine the individual concentrations of the reactants. In order to do
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Thus, the reaction orders remain valid. Next the value of ΔS2O8-2 was retrieved by dividing [S2O3-2] by 2, which was concluded to be 9.1x10-4 mol/L. Using the ΔS2O8-2 and the time it took for the reaction to complete, the rate was determined.
For trial 1, the rate of reaction was 1.61x10-5 mol L-1 s-1, k was 0.167 mol2 L2 s-1 and the ionic strength was 0.2362 mol L-1 s-1. For this reaction no electrolytes were added to speed up the reaction. The reaction run for 1 can be considered as the model reaction for this experiment, since other substances were not added in. For trial 2, the rate was 7.95x10-6 mol L-1 s-1, k was 0.331 mol2 L2 s-1, and the ionic strength was 0.1327 mol L-1 s-1. In this trial, the concentration of [S2O8-2] was reduced, while (NH4)2SO4 was added. The electrolytes from (NH4)2SO4 were able to diffuse, and replenish the reaction’s ionic strength. Thus, the k value was higher and the reaction was quick. For the third trial, the rate of reaction was 1.83x10-6 mol L-1 s-1, k was 0.305 mol2 L2 s-1, and the ionic strength was 0.1055 mol L-1 s-1. The concentration of S2O8-2 is ¼ of trial 1, thus the rate of the reaction also decreased, and the overall reaction took longer to finish. For the fourth
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