# Ex .5 Spectrophotometric Analysis of a Commercial Aspirin Tablet Standard solution and

Ex .5 Spectrophotometric Analysis of a Commercial Aspirin Tablet

Standard solution and Beers law calibration curve

1-Fill in the following table :

M1 x V1 = M2 x V2

M1= molarity of salicylic acid (SA) Volume of SA=V1

V2= the total volume of dilute solution =10mL

M2=molarity of dilute solution (u have to find) and write in table below

Solution

Absorbance(A)

Concentration /M

SA. 1 (V1=1.0)

0.159

SA .2 (V1=3.0)

0.356

SA.3 (V1=6.5)

0.589

SA .4 (V1=9.0)

0.879

ASA of unknown

0.641

( find from calibration curve)

2- Plot a graph (or calibration curve) of Absorbance vs. conc by using the values from the table

B) Analysis of unknown aspirin tablet

1. Mass of aspirin tablet =0.1205g

2. Concentration of ASA unknown from calibration curve =………………….. mol / L

3. Conc of Stock ASA unknown = 25 ml / 1.5 ml ( D.F ) x Conc. of ASA unknown(step 2) =………………… mol / L

4. Moles of ASA in 50 ml solution = Conc of Stock ASA unknown(step 3) x 50mL= ………….. moles

5.Mass of ASA = moles ASA x Molar Mass ASA (180 g / mol ) = …………………g

6. % of ASA in aspirin = Mass of ASA(step 5) / Mass of aspirin tablet(step 1) x100 = ………………….. % 