posted by John on .
An aspirin tablet weighing 0.502 g has been analyzed and contains 68.2 % ASA (180.16 g/mol) by mass. A student dissolved
the tablet in hot NaOH and the cooled solution was diluted with DI water to the mark in a 250 mL volumetric flask. Exactly 3.00 mL
of the solution was pipetted into a 100 mL volumetric flask and diluted to the mark with FeCl3 solution.
The concentration of the diluted solution is
68.2% of .502 g is 0.3424 g of ASA (acetylsalicylic acid). Divide that by 180.16 g/mole to get the number of moles of ASA. You end up with that many moles of ASA in the 250 ml flask.
3/250 of that number of moles of ASA ends up in the 100 ml flask, where it remains as the sample is further diluted. Divide that number by 0.100 liters for the molar concentration of ASA in the final solution.