Procedure external standards and a sample 1 1make a

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Procedure – External Standards and a sample1
1.Make a stock solution (1L of 100 ppm acetylsalicylic acid in 2% HCl). Make sure the acetylsalicylic acid is completely dissolved before you dilute to the mark. Invert the
2.Prepare a series of calibration standards of different concentrations of acetylsalicylic acid (0, 4, 6, 8, 10, 15, 20 ppm). Use your 100 ppm stock solution plus the dilution function (C1V1=C2V2) to make the standards. You need only 10 mL total volume of each dilution. All dilutions will be made to contain 2% HCl, even your blank. 3.Each student will have ONE 10-mL volumetric flask. These are expensive measuringdevices, not storage bottles. Once each solution is prepared and inverted well, transfer the contents to a clean, labeled test tube. Clean the flask and re-use it.4.Look at the bottle of Aspirin tablets and record the amount of active ingredient (acetylsalicylic acid) printed on the label. Examine your dilutions table and design a procedure to dissolve and dilute your entire tablet in such a way that the final, theoretical concentration will be 10 ppm acetylsalicylic acid. Transfer a portion of your diluted unknown into a clean, labeled test tube. Remember, all dilutions are to contain 2% HCl. (Wet solid with methanol to increase solubility)Procedure – Standard Addition Method5.To a clean 10.00-mL volumetric flask, spike in enough 100.0 ppm acetylsalicylic acid standard stock solution to make the knownspiked final concentration 10.00 ppm. 6.Add to the volumetric flask in 5, the same volume of the aspirin tablet solution (1L) that you used to prepare the unknown in number 4. Dilute to the mark with 2% HCl.7.You will now have a solution that is approximately 10ppm from the unknown plus exactly 10.00 ppm from the ASA stock solution.

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