[adenine135]

In an experiment where spectrophotometry is used to determine to concentration of ASA in an aspirin tablet:

Explain why the FeCl₃-KCl-HCl solution was used as a reference solution. Suggest a procedure you could follow to determine whether it was necessary to use this solution as a reference or whether distilled water would have been just as satisfactory.


This is what I have so far:

Often several components of a solution absorb energy of the wavelength being used for the analysis. To compensate for this interference, a reference solution is prepared and the spectrophotometer is set so that 100% of the light of the chosen wavelength is transmitted by the reference solution.

So I think the FeCl₃-KCl-HCl plays a part in the production of aspirin... but not exactly sure how.

[Nicolas88]

No FeCl3-KCl-HCl is not used for the production of aspirin.

didn't you dissolve the aspirin in FeCl3-KCl-HCl soln ?
now that you have a solution of "aspirin + FeCl3-KCl-HCl" the spectrophotometer will give you the absorption of the aspirin AND FeCl3-KCl-HCl and you dont want that ,you only want the absorption of aspirin alone , thats why you will need to use FeCl3-KCl-HCl solution as reference sample.

To understand it more i will give you this example :
lets say you want to weigh a salt that is in a 50-ml beaker..if you weigh it as it is it will give you the weight of the salt + beaker , so what you do is put the empty beaker and tare then put the salt so you have the weight of the salt alone.