Aspirin Analysis
# 24
What are we doing today
• We are going to use a spec. 20 to determine the
absorbance of our tablet.
• Once we know the absorbance we can determine the
strength of our aspirin .
• Remember use the equation of line.
• To help determine the absorbance, we complex the
aspirin.
Procedures
• Obtain, wash, and dry with acetone a mortar and pestle
• Obtain and accurately determine the mass of a aspirin tablet.
• Grind up your aspirin and place it in a 125 mL. Erlenmeyer flask.
• Add 10 Ml. Of 1. M NaOH and about 70 mL. Di. H2O
•Place the flask on a hot plate and warm the solution
while
swirling.
•Warm the solution until it boils.
•Rinse the flask down with Di. water
•Filter the solution into a 250mL. round bottom flask.
•Mix very thoroughly.
Procedures Continued
• Pipette 1 mL. of your solution into a 25mL.
graduated cylinder.
• Add 0.020M IronIIIChloride solution and
fill to the 20mL. line.
• Mix thoroughly
• Follow procedures on spec. 20 to
determine absorbance.
Table 24-1 Calibration Graph Data
M of Complex X 104
.898
Absorbance
.146
1.78
.310
2.660
.470
3.550
.620
4.440
.780
Remember .898 actually means .898 X10-4
Lou Tisone
Chem116-30
Fall-06
Absorbance
Molarity Vs. Absorbance
y = 0.1782x - 0.0099
1
0.5
0
0
1
2
3
Molarity X10+4
4
5
Due Next Week
• Two graphs #1 absorbance Vs. M x104
from the data I gave you
• # 2 Abs Vs. Mg./ Tablet you must calculate
• Do two trials ( two different tablets)
• Complete table 24-2
• Answer questions 2-4
Lou Tisone
Chem116-30
Fall-06
Absorbance
Mg of Aspirin Vs. Absorbance
y = 0.002x - 0.0097
1
0.5
0
0
100
200
300
Mg. of Aspirin
400
500
Help with table 24.1
Convert from Molarity to mg/tablet
Ex #1 .898X10-4
4
.898x10 moles .250L 180g 1000mg
20
1L
1tablet mole
1g
 80.82mg/Ta blet
You must do the same for the rest of the
data so you can make the second graph
Table 24.2 Trial # 1
Mass of my aspirin is .370grams, and abs = .482
from my calibration graph # 1 y = 0.1759X-0.0015
.482X  0.0015
X
0.1759
X  2.76M
Don’t forget X10-4
the actual answer = 2.76X10-4 M
Mg Aspirin / Tablet table 24.2
2.76x10 4 moles .250L 180g 1000mg
20
1L
1tablet mole
1g
 248.4mg/Tablet
Percent Aspirin / Tablet
Weight of entire tablet = 0.370g or 370mg
248.4mg/Ta blet
X100  67.02% Aspirin
370mg/Tabl et