Chem162_Kinetics_Report_032410_000 (1) Sheet1

Chem162_Kinetics_Report_032410_000 (1) Sheet1 - Page 1 of...

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Page 1 of 11 Name and ID: Anders Conway Quiz Section: AC Lab Partner: Jordan Cox Grading: 60 pts. (Lab notebook pages are worth 5 pts - total for report and notebook is 65 pts) Experiment 2: Chemical Kinetics Part I: A Clock Reaction Part II: Crystal Violet-Hydroxide Reaction Note: All sections of this report must be typed. By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will cost you 5 points. Signature: Purpose and Method Part I: Clock Reaction (3 pts) (purpose, reactions/rate law, method) The purpose of part one is practice the determination of the order of the reaction with respect to each reagent, the rate constant and the activation energy through experimentation by the method of initial rates. We will also add a catalyst and observe its effect on the rate constant and activation energy. We will observe and evaluate the reaction BrO 3 - (aq) + 6I - (aq) + 6H 3 O + (aq) --> Br - (aq) + 3I 2 (aq) + 9H 2 O (l) . The Rate law will follow the form: rate = k[BrO 3 - ] b *[I - ] i * [H 3 O + ] h . To determine the rate we will observe how long it takes this reaction to go to completion by adding a starch indicator (starch and iodine create a blue-pigmentation) and adding a small amount of S 2 O 3 2- (aq) (thiosulfate). The thiosulfate reacts with the I 2 and reduces it to I - (I 2(aq) + 2S 2 O 3 2- (aq) --> 2I - + S 4 O 6 2- ). This delays the accumulation of I 2 molecules that react with starch to produce the indicatory blue coloration. We complete many runs of this reaction with these reactants, varying the concentration of each reagent while holding the concentration of S 2 O 3 2- constant. By measuring the time it takes for the blue coloration to appear and knowing the stoichiometric ratios of reactants and S 2 O 3 2- , we can determine the rate orders for each reactant. I have described the mathematical process for determining the rate order of I - below: If rate = k[BrO 3 - ] b *[I - ] i *[H 3 O + ] h , let k'=k[BrO 3 - ] b *[H 3 O + ]. Then, rate = k'[I - ] i . Thus, log(rate) = log (k') + i*log(I - ). If this last equation is graphed, i is the slope of the line. We will also add a catalyst (MoO 4 2- (aq) ) and alter the temperature of the solutions to measure the effect this has on the rate. Varying the temperature also allows us to calculate the Activation Energy (Ea) by means of the following equation: ln(k 2 /k 1 ) = -(Ea/R)*(1/T 2 - 1/T 1 ). We will do so for both the solutions, with and without catalyst. Part II: Crystal Violet-Hydroxide Reaction (3 pts) (purpose, reactions/rate law, method) In part two we use the integrated rate approach to calculate the rate order and constant for the reaction between Crystal Violet (CV + ) and Hydroxide (OH - ). The reaction is as follows: CV + + OH - --> CVOH. We will set up our reaction such that the concentration of OH- is far greater than that of CV+. Thus rate = k[CV+]c*[OH - ] 0 , let k'=k[OH - ] 0.
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Chem162_Kinetics_Report_032410_000 (1) Sheet1 - Page 1 of...

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