The following data was collected to determine the rate constant and reaction ord

Question

The following data was collected to determine the rate constant and reaction order for a theoretical reaction in which chemical A, chemical B, and the iodide ion (I-) react to form chemical C and iodine (I2). A + B + 2I- --> C + I2 [1] The generalized rate equation for this reaction would be represented by Rate = k[A]a[B]b[I-]c [2] The reaction above is much slower than the reaction between iodine and the thiosulfate ion (S2O32-) so there is not an appreciable amount of I2 present as long as there is thiosulfate ion available. Once all of the thiosulfate ion reacts, the iodine present will form a complex with a starch indicator that results in the solution turning dark blue. I2 + 2S2O32- --> 2I- + S4O62- [3] Since the concentration of thiosulfate ion is small in all of the following trials, the concentrations of the reactants in reaction [1] remain essentially unchanged during the period studied. In the data below, the time to completion is the amount of time between when the chemicals are mixed together and when the solution changes color due to the thiosulfate ion being depleted. Trial 1 - Temperature = 25.0oC - Molarity of A = 0.100 M - Molarity of B = 0.100 M - Molarity of I- = 0.100 M - Molarity of S2O32- = 0.0010 M - Time to Completion = 40 seconds Trial 2 - Temperature = 25.0oC - Molarity of A = 0.200 M - Molarity of B = 0.100 M - Molarity of I- = 0.100 M - Molarity of S2O32- = 0.0010 M - Time to Completion = 20 seconds Trial 3 - Temperature = 25.0oC - Molarity of A = 0.100 M - Molarity of B = 0.200 M - Molarity of I- = 0.100 M - Molarity of S2O32- = 0.0010 M - Time to Completion = 10 seconds Trial 4 - Temperature = 25.0oC - Molarity of A = 0.100 M - Molarity of B = 0.100 M - Molarity of I- = 0.200 M - Molarity of S2O32- = 0.0010 M - Time to Completion = 14 seconds Trial 5 - Temperature = 35.0oC - Molarity of A = 0.100 M - Molarity of B = 0.100 M - Molarity of I- = 0.100 M - Molarity of S2O32- = 0.0010 M - Time to Completion = 20 seconds A)How much does the concentration of chemical A change in each of the trials? Report you answer in moles/liter, but do not include units in your answer. B)What is the rate in Trial 1 above? C)What is the order of the reaction with respect to chemical A? D)What is the order of the reaction with respect to I-? E)What is the value of the rate constant in Trial 1? F)What is the value of the rate constant in trial 5? G)Estimate the value of the activation energy for reaction [1] using the Arrhenius equation.

Explanation / Answer

k = 100.15/(1.0 x 10^13) = 1.0 x 10^-11 M^-1 s^-1

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