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Unformatted text preview: Chemical Kinetics Author: Holly Polk Lab Partners: Erica Geggie, Anna Giroux, Guzyal Gabitova Instructor: Janel Michels Chemistry Lab 152, Section 004 Date Work Performed: September 15 and September 22, 2008 Date Report Submitted: September 29, 2008 Abstract The objective for the chemical kinetics lab is to determine the rate law for the bleaching of a food dye by performing a reaction while collecting absorbance and time data. Techniques include making dilutions of dye and bleach and measuring the concentration levels with a spectrophotometer. The final result of the experiment was a rate law equation of: rate = .0096[dye] 1 where the rate constant K was .0096 1/s, the order of dye was 1, and the order of bleach was 0. For the hypothesis, it was expected that the concentrations of the reactants would decrease over time, and the rate order would be greater than 1. The hypothesis was not met because the order was only 1. Introduction The objective for the chemical kinetics lab is to determine the rate law for the bleaching of a food dye by performing a reaction while collecting absorbance and time data. The reaction involves bleaching a food dye with the common household bleach (sodium hypochlorite, NaOCl) while measuring dye concentration with a spectrophotometer. In order to determine the order of the reaction and the rate constant, k, the experimental reaction will be ran a number of times using different concentrations of reactants. After obtaining the experimental data, the rate law can be determined, where the rate is set equal to a constant, k, and multiplied by the concentrations of all reactants in the rate- determining step. The order of the reactants in the equation will also be determined based on proportionation, or measuring change in concentration over time of a reactant while keeping the other reactant constant. The order can also be determined by the integrated rate equations, which entails plotting the data and finding the one that produces a linear plot. The rate constant, k, incorporates the effects of the temperature and catalyst, which will be constant. The average rate of the equation is the change in concentration over the change in time. The rate constant is the rate over the concentration of the reactant. Rate constants can be determined from every trace of data points by finding the rate value and the corresponding concentration of reactants. Afterwards, an average K value can be calculated and a standard deviation may be computed. Reaction rate is important because it tells how much time it will take a reaction to complete and this information is required in industry, scientific works, research, medicine, and engineering. For example, knowing the rate of a medicines breakdown in the human body would allow a doctor to calculate how much of a medicine someone should take over a certain time period. For the hypothesis, it is expected that the concentrations of the reactants will decrease over time, and the rate order would be greater than 1.the rate order would be greater than 1....
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