Question

Aspirin is acetylsalicylic acid (ASA) ( C₉H₈O₄). It reacts with NaOH ( a base) to produce salt (sodium acetylate) and water. Both Aspirin and NaOH react in 1:1 molar ratio, as

              C₉H₈O₄ +         NaOH     →       NaC₉H₇O₄     +        H₂O

So, moles of NaOH = moles of ASA

• Or, mmol of of NaOH = mmole of ASA           ; mmol is milli mol
• and mmole of NaOH = Molarity of NaOH * Volume of naOH used (in ml)

                                  = (0.1177 M) * (Vf -Vi) ml = mmol of Aspirin or ASA

• mmol of ASA are reported in the table upto 4 decimal places.

Molar mass of aspirin = 180.16 g/mol

• So, mass of aspirin or ASA (in mg) = Molar mass of Asprin * mmol of Aspirin

                                                        = (180.16 g/mol ) * (0.1177 M) * (Vf -Vi) ml

• % acid in tablet = {(mass of ASA in mg)/ ( wt. of tablet in mg)} *100
• Note that tablet contains some starch binders also along with aspirin which does not react with NaOH.

Since, claimed mass of ASA present = 324 mg,

• % error = [{(mass of ASA in mg) - (324 mg) } / 324 ] * 100

The table is calculated using excel spreadsheet.

Note that in first row, weight of tablet is noted in terms of mg.

Wt. of ASA tablet (in mg) Initial volume reading (ml) final volume reading (ml) volume used moles of NaOH moles of ASA in flask mass of ASA in mg % acid in tablet error % error = (error *100) Trial 1 Trial 2 Trial 3 Trial 4 396 372 375 388 0 15.45 33.17 0 15.85 33.17 48.92 15.53 15.85 17.72 15.75 15.53 1.865545 2.085644 1.853775 1.827881 1.8655 2.0865 1.8538 1.8279 336.0885 375.9038 333.9806 329.3145 84.87083 101.0494 89.0615 84.87486 0.03731 0.160197 0.030804 0.016403 3.731012 16.0197 3.080435 1.640267

Question. Lab Report

For the aspirin runs, which trial should be discarded? Why? Compare the tablet contents to each other and to the Walgreen’s claim. Are you getting your money’s worth? Is the manufacturer playing fair and following the FDA guidelines? How important is this, considering the tablet contains aspirin?

Answer 1

Trial 2 should be completely discarded completely as the mass of ASA in mg is far away from the claim value 324 mg. However, other values still lie closer.

The other value lie closer to 324 mg, but even a small excessive or lesser amount than the required value can lead to bad health. Higher dose can lead to side effects and lower dosage can not work properly to cure disease. Hence, the manufacturers should be very careful about the dosage value of aspirin.

However, if the manufacturers are not giving the claimed dosage, they are definitely cheating the customers.