Question

the determination of aspirin in commercial preparations experment explain why the FeCl3-KCl-HCl solution was ased 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 satifactory

Answer 1

The concentration of acetylsalicylic acid (ASA) is determined spectrophotometrically by measuring absorbance of visible light at a given wavelength.

A= ecl ;

Where e = Molar absorptivity of the particular absorbing species in (L /moles cm)

l = Pathlength of the light through the solution in cm

c = Concentration of the absorbing species in moles/L

Acetylsalicylic acid (ASA) complex ion, is formed by hydrolyzing the aspirin sample (ASA) and complexing it with Fe³⁺ ion in FeCl3-KCl-HCl solution to bring out the color as shown in the chemical reaction. The complex displays a maximum absorption at a wavelength of 530 nm, and has a crimson red color

The spectrophotometer will give the absorption of the aspirin and FeCl₃-KCl-HCl and in order to get the absorption of aspirin alone, FeCl₃-KCl-HCl solution is used as reference sample.