aspirin tablets are insoluble. 14. Quantitatively transfer the resulting solution to a 250-mL volumetric flask using a funnel and wash bottle. Dilute with water to the 250.00 mL mark. 15. Perform a gravity filtration on about 20 mL of this cloudy solution using a long stemmed funnel. The filtrate should be clear. 16. Pipet 2.00 mL of this clear solution into a 50-mL volumetric flask and dilute to the 50.00 mL mark with the acidified 0.02 M iron(III) chloride solution. 17. Measure the mean absorbance of this solution as outlined in steps 8 and 9 and record the value in your lab notebook. Make sure that the colorimeter reads 0.000 absorbance for the acidified 0.02 M iron(III) chloride solution. If it does not, you will have to re-calibrate the colorimeter as in step 6. 18. Calculate the concentration of the salicylato iron(III) complex in this solution using the slope of the line of the graph that you plotted in Part A. Then calculate the concentration of the acetylsalicylic acid (in the 250-mL volumetric flask), the moles of acetylsalicylic acid, and the mass of acetylsalicylic acid in the tablet and compare it with that on the bottle. Consult with your lab instructor if necessary. 19. At the end of this part of the experiment, all solutions may be disposed of in the waste container. Rinse thoroughly all pipettes, flasks, and cuvettes and return them to their original location. 20. Delete any stored data from the computer interface by tapping the “File” menu with the stylus and selecting “New”. The LabQuest should be left turned on for the next lab section. If the lab is scheduled to end at 4:50 PM or 8:20 PM then the LabQuest should be turned off by pressing the silver button on the top left of the device. 21. Hand in a copy of your data (recorded in your lab notebook) to your lab instructor.
6 DATA SHEET PART A Mass of acetylsalicylic acid ____________ Volume of solution prepared ____________ Concentration of tetraaquasalicylato ion in Solution S ____________ (show calculation to the right) Volume of Solution S Concentration Absorbance( mean ) Solution 1 ___2.00 mL___ ____________ ____________ Solution 2 ___3.00 mL___ ____________ ____________ Solution 3 ___4.00 mL___ ____________ ____________ Solution 4 ___5.00 mL___ ____________ ____________ Solution 5 ___6.00 mL___ ____________ ____________ Show calculation for concentration of Solution 1: Attach a plot of absorbance ( y -axis) vs. concentration ( x -axis). Use Excel and its features to draw a straight line through the points and to calculate the equation of the line which should be displayed on the graph. Equation of straight line _________________________________ PART B Brand of Aspirin tablet ____________ Mass of acetylsalicylic acid per tablet (from label on bottle) ____________ Absorbance (ave.) of solution ____________ Concentration of acetylsal