An aspirin tablet weighing 0.475 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
0.475 g aspirin x 0.682 = g ASA.
That amount was placed in 250 mL beaker so the concn (in grams) = g ASA/250 mL.
Perform that division and you have g ASA/mL. Now you dilute it 3:100; therefore, the new concn is
g ASA/mL x (3 mL/100 mL) = g ASA/mL in the new solution. If you want molarity, you will need to convert to moles/L.
To determine the concentration of the diluted solution, we need to calculate the moles of ASA (acetylsalicylic acid) in the original tablet solution and then divide it by the volume of the diluted solution.
1. Calculate the number of moles of ASA in the tablet:
First, we need to calculate the mass of ASA in the tablet. As per the given information, the tablet weighs 0.475 g, and it contains 68.2% ASA by mass.
Mass of ASA in the tablet = 0.475 g × 0.682 = 0.32435 g
Next, we convert the mass of ASA to moles using the molar mass:
Molar mass of ASA = 180.16 g/mol
Number of moles of ASA = Mass of ASA / Molar mass of ASA
= 0.32435 g / 180.16 g/mol
2. Calculate the concentration of the diluted solution:
Given that exactly 3.00 mL of the original solution was pipetted, and it was diluted to 100 mL with FeCl3 solution, we can assume that the final volume is 100 mL.
Now, we divide the number of moles of ASA by the volume of the diluted solution to calculate the concentration:
Concentration = Number of moles / Volume
= (Number of moles of ASA / Volume of the original solution) / Volume of the diluted solution
= (0.32435 g / 180.16 g/mol) / 0.100 L
Note: We convert mL to L by dividing by 1000, as 1 L = 1000 mL.
Finally, you can calculate the concentration using this equation.