Definitions of Group Report and/or Group ExperimentChemistry 20L Fall 2006Post-lab Report MUST be written inside your lab notebookPost-lab ReportChemistry 20L Fall 2006CHEM 20L Fall 2006 Before attempting to work on the group post-lab report, please take a moment and read the following items carefully. Definitions of Group Report and/or Group Experiment (1) All members in the group MUST contribute equally when working on the experiment as well as writing the post-lab report (2) Each group member must prepare ahead of time when writing the reports. This means review materials from lectures or from your Chemistry textbook or from on-line resources on certain topics that are relevant to the concepts when writing the reports. Contribution to the group work is meaningless if a group member does not understand the concepts behind the experiment. (3) It is the responsibility of the group members to plan ahead on when they should get together to work on the report. In other words, maintain good communication between group members. (4) It is the responsibility of each group member to honestly describe the work that they did during the experiment and in writing the report. No one should take advantage of the other group member. Report to the course instructor or your TA if you feel that other group members are taking advantage of your work. (5) Each member in the group MUST understand the concepts behind the ENTIRE experiment regardless of which portions of the report or experiment a person is responsible for. This is especially important for the exams.Chemistry 20L Fall 2006 Report Guidelines for Kinetics Study of Red Food Color with Bleach (The Assignment is provided as a handout.) Post-lab Report MUST be written inside your lab notebook Post-lab Report (This is a GROUP report. TURN IN ONLY ONE POST-LAB REPORT PER GROUP. ) Use the Kinetics Excel Tutorial as your guide when plotting the various graphs for this report. You will be expected to present the data and graphs for this report in the format described in the tutorial. Introduction: In a brief introductory paragraph or organized table indicate what each person was responsible for in both the performance of the experiment and the report. Each person must sign the report next to the description of his or her responsibilities. Data Calculations and Discussion: Serial Dilution • Provide a table for your final serial dilution procedure including the measured absorbance of each solution and the calculated molar concentration. The molecular weight of FD&C Red #3, which is 879.9 g/mol. Briefly describe any changes you made from your original plan. Rate Trial Scheme • Provide a table of your final rate trial scheme with a brief description of any changes you made from your original plan. Rate Trials • Using Beer’s Law, A = εbc, determine the molar absorptivity for FD&C Red #3. You may assume the diameter of the culture tube (that is, the path length) is 1.00 cm. • Calculate the initial concentration of dye in each rate trial. This is the concentration at time = 0 • Set up a spreadsheet table for each trial that you used for analysis. Make sure the headings for each table reflects the experimental conditions for the trial. Label the columns, time, Absorbance, [dye], ln [dye], 1/[dye]. Note: [ ] means concentration in mol/L. • Calculate the data for each cell. (Note: Use the measured absorbance of the solution during the trial, the calculated extinction coefficient for the dye, and a path length of 1cm to determine the [dye] during the rate runs.)Chemistry 20L Fall 2006 Report Guidelines for Kinetics Study of Red Food Color with Bleach (The Assignment is provided as a handout.) Briefly explain, if applicable, why trials that you performed were not used in the subsequent analysis. Using your spreadsheet data, prepare three graphs for each trial: • [dye] vs. time • ln[dye] vs. time • 1/[dye] vs time. Be sure to title your graphs, and label the axes including units. EACH of your graph MUST include a legend for the experimental condition of EACH TRIAL. Print EACH graph on a separate piece of paper. Rate Data Analysis: • From a visual inspection of these plots, select the linear relationships to establish a, the order of the reaction with respect to the dye. Explain how you arrived at your value. • By comparing the slopes of the lines for various trials, determine b, the order of the reaction with respect to hypochlorite. Refer to page 2 and 3 of the handout on how to estimate the value of “b”. • If sufficient data is available, calculate the average value for b, the order of the reaction with respect to hypochlorite and the percent relative error. “ • Using the plots that give linear relationships and the values for a and b you obtained, determine the rate constant (k) for each trial. Refer to page 2 and 3 of the handout. Error Analysis: • Calculate the average value for your rate constants and the percent relative average deviation. • Is your range of values for b consistent with a “whole number” for the order of the reaction? • If you have only one value for b, what percent error would let you deduce that experimentally this is a “whole number?” Conclusions: Summarize your results and the justifications for using the plots you did to determine the order of the reaction. Write your experimental rate law based on the order of the dye and the order of the sodium hypochlorite that you obtained in your calculations. Kinetics studies can disprove a proposed mechanism, but can never prove a mechanism. Explain whether the results that you have obtained are consistent with the mechanism proposed on page 2 of this
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