A Colorimetric Determination of Aspirin in Commercial Preparations - Laboratory Guide
You will not be allowed to bring your lab manual to class with you for this experiment. Be prepared to do the experiment only using this Laboratory Guide and your TA for guidance. Record any data that you need to record on these yellow sheets and turn them in as your post-lab report.
Part 1 Prepare the Beer's Law Plot
To make the Beer's Law plot, you will prepare a series of five standard solutions of known concentration of acetyl salicylic acid (ASA, the active ingredient in aspirin) and measure their absorbances at 530nm.
First, prepare the stock solution of ASA.
Weigh 0.1g of ASA to the nearest mg.
Transfer quantitatively to a 50mL Erlenmeyer flask.
Add 5 mL of 1M NaOH.
Heat to boiling on a hot plate. Then, turn off the hotplate.
Transfer quantitatively to a 50mL volumetric flask and dilute to the mark with distilled water. This is your stock solution that will be used to make your standard solutions. Calculate the concentration of ASA (M.W. 180.2g) in this solution.
Second, prepare the five standard solutions. Use the FeCl3-KCl-HCl solution to dilute your stock solution.
Dilute 0.1 mLs of stock solution to 10mLs. What is the molarity of ASA in this solution?
Dilute 0.2 mLs of stock solution to 10mLs. What is the molarity of ASA in this solution?
Dilute 0.3 mLs of stock solution to 10mLs. What is the molarity of ASA in this solution?
Dilute 0.4 mLs of stock solution to 10mLs. What is the molarity of ASA in this solution?
Dilute 0.5 mLs of stock solution to 10mLs. What is the molarity of ASA in this solution?
Third, measure the absorbance of each standard solution at 530nm using the spectrometer.
Fourth, analyze your data.
Prepare a table of the data that you will use for your Beer's Law Plot. Show the data on this page.
Plot the data in the computer lab using Kaleidagraph. Attach the graph to this page.
Obtain a linear fit and the equation for the line.
A Colorimetric Determination of Aspirin in Commercial Preparations - Laboratory Guide
Part 2 Analyze an Aspirin Tablet
You will determine the amount of aspirin in an aspirin tablet. Repeat this procedure twice.
First, prepare the solution that you will analyze.
Weigh 0.1g of the unknown to the nearest mg.
Transfer to a 50mL Erlenmeyer flask.
Add 5 mL of 1M NaOH.
Heat to boiling on a hot plate. Then, turn off the hotplate.
Transfer quantitatively to a 50mL volumetric flask and dilute to the mark with distilled water.
Dilute 0.50 mLs to 10 mLs with the FeCl3-KCl-HCl solution.
Second, measure the absorbance of your solution.
Third, make the following determinations:
Determine the concentration of ASA in your solution using the Beer's Law plot.
Determine the grams of ASA in your solution.
Determine the grams of ASA in your sample.
Determine the % weight of ASA in your sample.
Fourth, repeat the procedure.
Determine the concentration of ASA in your solution using the Beer's Law plot.
Determine the grams of ASA in your solution.
Determine the % weight of ASA in your sample.
Finally, determine the average % weight of ASA in your sample from your two determinations.
Back to help with Colorimetric Determination of Aspirin.
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Last updated: 18-September-01 / lav