[Babygal]

I did an experiment on measurement of the active ingredient in aspirin pills..

My filtrates volumes were:


6.3 ml
7.9 ml
8.9 ml
12.6 ml

The absorbance reading was at 525nm. The questions are as follows:

Using the Beer-lambert law to calculate the concentrations of salicylic acid in your filtrates (don't forget the various dilutions you have made). molar absorptivity (e525 = 949 L mol-1 cm-1)

My absorbance reading were:

2.834, 1.023 (dilution factor = 1:400), 3.311, 3.436 (dilution factor = 1: 4).


My concentrations were as follows: 2.886 e-3M, 1.078e-3M, 3.489e-3M & 3.621e-3M.

 However, I am confused by the statement that says: don't forget the various dilutions you have made). Does this mean I have to multiply the concentrations I got with the dilution factor?

I am also stuck on the questions that says:

1. From these concentrations, use the RMM of acetylsalicylic acid to convert this to a total weight in your filtrates, and hence per tablet.
2. How does this compare to a) the claimed content and b) the indirect determination?
- The manufacture's aspirin was 300mg (0.3g) and mine was (0.2920g).

3. How does 0.2920g compare to the manufacturer's statement i.e. 0.3g? Think about the possible reasons fo any differences observed.

 Please tell me where I am going right and wrong and what I need to do in the next calculations. Thanks. I am so confused right now cause if I don't get 70% I will fail the course:(