Rainey_Experiment 2

Rainey_Experiment 2 - Experiment 2: Effects of Ionic...

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Experiment 2: Effects of Ionic Strength on the Kinetics of the Reaction of Crystal Violet with Hydroxide Ion Author: Ben Rainey Group 2 Section 3, T 2:00 PM – 5:00 PM Partner: Ben Huffer September 21, 2010 Abstract : In this experiment, the main focus was to determine the kinetics of the reaction between crystal violet and hydroxide ion. The significance of ionic strength regarding this reaction was also determined. The goals of this experiment were to evaluate the reaction order with respect to both crystal violet and hydroxide ion, and to determine the specific rate constant for the reaction as a function of ionic strength. To accomplish these goals a Jenway Model 6405 UV-Vis Spectrophotometer was utilized to measure absorbance. Reaction order was then evaluated by comparing linear regression values. The specific rate constant for the reaction was determined by utilizing the relationship between hydroxide ion concentration and the pseudo rate constant. The reaction was found to be third order overall, second order with respect to crystal violet and first order with respect to hydroxide ion. The average specific rate constant for the reaction was found to be 2.82 x 10 6 mol -3 L 3 min -1 . The overall rate law expression is given by: = [ +] [ -] rate k CV 2 OH . It was determined that as ionic strength increased, reaction rate decreased. The proposed reaction mechanism was found to be valid within thirty-eight percent for the reaction through testing the dependence of the rate constants on the activities of the ions in the solutions.
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Experiment 2: Effects of Ionic Strength on the Kinetics of the Reaction of Crystal Violet with Hydroxide Ion I. Introduction There were two main objectives for this experiment. The first objective was to determine the reaction order with respect to both crystal violet and hydroxide ion. The second main objective was to determine the effect of increasing ionic strength on the kinetics of the reaction, specifically the reaction rate. Chemical kinetics is the study of reaction rates. In aqueous solutions, crystal violet exists as a positively charged ion. The resonance structures that crystal violet exhibit indicate an electron deficiency at the tertiary carbon. When reacted with negatively charged hydroxide ions, the hydroxide attacks this tertiary carbon, forming the colorless carbinol derivative. The reaction involves two oppositely charged ions. Therefore, the kinetics of the reaction will theoretically be sensitive to the ionic strength of the solution and exhibit a primary salt effect. Concentration, c, will be obtained from the raw absorbance readings, A, using the relationship shown in the Beer-Lambert law: = = A logI0I εcd (2-1) where I 0 /I is the fraction of light transmitted, d is the cell path length, and ε refers to the molar absorption coefficient. The general rate law for this experiment is: = [ ] [ ] Rate k CV n OH m (2-2) Under the experimental conditions present, k[OH] m is a constant term, which allows
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This note was uploaded on 03/08/2011 for the course CHEM 232 taught by Professor James during the Spring '11 term at Clemson.

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Rainey_Experiment 2 - Experiment 2: Effects of Ionic...

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