Kineticsexperiment

Kineticsexperiment - THE REACTION OF RED FOOD COLOR WITH BLEACH TECHNICAL AND THEORETICAL SKILLS In this assignment you will prepare volumetric

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20L: Summer 06 1 T HE R EACTION OF R ED F OOD C OLOR WITH B LEACH T ECHNICAL AND T HEORETICAL S KILLS In this assignment you will prepare volumetric solutions carry out a serial dilution procedure determine the extinction coefficient of a compound monitor the rate of a chemical reaction use a spreadsheet to analyze data calculate the order and rate constant of a reaction S AFETY FD&C Red #3, or Erythrocin B sodium, the food coloring dye that you will use in this experiment is intensely colored. Always wear safety glasses or goggles and a protective lab coat or apron. Handle the dye carefully avoiding spilling on the balance or bench top. Sodium hypochlorite, household bleach, is a bronchial irritant. Keep solutions covered or in the hood; avoid breathing the vapors. Immediately, wipe any spills of either reagent and wash any residues with large quantities of water. I NTRODUCTION In this assignment, you will prepare a solution of FD&C Red #3 (Red #3) and study its rate of reaction with sodium hypochlorite. Since this reaction is very visible, you will use a spectrophotometer to quantitatively follow the rate of disappearance of the colored reagent. Your rate data will allow you to determine the rate law and to propose a possible mechanism for the reaction. FD&C #3 Because of the extended conjugation of alternating double bonds within the molecule, the π−π * absorption occurs in the visible region of the spectrum at 530 nm. When the dye reacts with hypochlorite, the color disappears. Even though the product of this reaction has never been determined, we can carry out rate studies with the reagents to determine the mechanism that occurs. One possible explanation for this reaction is that the bleach oxidizes the central methylene carbon so that the molecule no longer has the extended conjugation system and the π−π * absorption of the less conjugated product occurs at a lower wavelength outside of the C O I NaO I COONa I O I
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20L: Summer 06 2 visible region of the spectrum. The product might be the alcohol (II) compound depicted in the reaction on the next page. A study of how the concentrations of the reactants affect the rate of the reaction gives insight into the mechanism and whether this simple explanation might be correct. Red Colorless? The Rate Law The rate of a reaction can be represented either by the disappearance of reactants for the appearance of products. Since Red #3 is the only colored species in the reaction, we can monitor the rate of the reaction shown above by recording the decrease in the color of the solution with time. That is, Rate = ! d [Red #3] dt = k [Red #3] a [OCl - ] b (1) where the exponents a and b indicate the molecularity or order of the reaction with respect to each reagent, and k is the overall rate constant for the reaction at room temperature. The objective of this experiment is to determine the values of the exponents a and b and the value of k at room temperature.
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This note was uploaded on 04/24/2008 for the course CHEM 20L taught by Professor Gould during the Spring '08 term at UCLA.

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Kineticsexperiment - THE REACTION OF RED FOOD COLOR WITH BLEACH TECHNICAL AND THEORETICAL SKILLS In this assignment you will prepare volumetric

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