Chemical Kinetics Formal report (2) - Chemical Kinetics a...

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Chemical Kinetics, a Clock Reaction David Liu Chemistry 102, Los Angeles City College, 855 North Vermont Avenue, Los Angeles CA 90029 March 05, 2015
Abstract This experiment was done by monitoring the reaction between Iodine and thiosulfate that will result in a blue color indicating that the desired amount of I 2 has been created with varying concentrations of the reactants. By doing so, basically the color change is similar to a clock system that monitors the amount of Iodine products formed, which is the consistent amount of thiosulfate that is added in each experiment, the thiosulfate in this experiment will be considered the limiting reagent. After all thiosulfate has all been reacted, the excess Iodine will react with the starch to turn the reaction blue, hence the thiosulfate in this experiment is functioning just as a clock counting down the same amount of Iodine that is being reacted in each trial. Further investigating the reaction rate that is dependent upon temperature, by using the same amount of concentration of [I - ], [BrO 3 - ], and [H + ] at varying temperatures from 0 o C to 40 o C. The final part of the experiment will be adding a catalyst, ammonium molybdate (NH 4 ) 2 MoO 4, to the reaction to discover that it accelerates the reaction by approximately 10 times. The purpose of the this experiment is to determine the reaction order of each reactants I - , BrO 3 - , and H + , which were found to be 1, 1, and 2 accordingly. The average rate constant k was determined to be 25.8s -1 , while the activation energy E a was determined to be 27.0 kJ/mol, and since the reaction order of each reactants are 1, 1, and 2, the overall reaction order was determined to be 4. Introduction Reaction rates of a chemical reaction are extremely important in the field of chemistry and application to daily use, without the precise calculation of reaction rates, chemicals cannot successfully react thus producing the necessary reagents for all life forms. This experiment is an introduction to method of calculating reaction rates, known as chemical kinetics which involves the determining the influencing factors that affects the rates of reactions, such as temperature, concentration and the addition of a catalyst to the reaction. Since there are three influencing factors, there will be three different parts of the experiment, each focusing on different influencing factors. Before determining the rate law of each reaction, the experimenters would first need to look at the reaction given, with most general reactions looking like below:
aA + bB  cC + dD (1) From this reaction, the experimenter can derive the rate law by employing the equation: Rate = k[A] x [B] y (2) In this equation, the [A] and [B] are the concentrations of the corresponding reactants whereas x and y are the relative reaction orders.

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