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

Remember .898 actually means .898 X10-4

M of Complex X 104 Absorbance

.898 .146

1.78 .310

2.660 .470

3.550 .620

4.440 .780

Lou TisoneChem116-30Fall-06

Molarity Vs. Absorbance

y = 0.1782x - 0.0099

0

0.5

1

0 1 2 3 4 5

Molarity X10+4

Ab

so

rba

nc

e

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

Mg of Aspirin Vs. Absorbance

y = 0.002x - 0.0097

0

0.5

1

0 100 200 300 400 500

Mg. of Aspirin

Ab

so

rba

nc

e

Lou TisoneChem116-30Fall-06

Help with table 24.1

Convert from Molarity to mg/tabletEx #1 .898X10-4

blet80.82mg/Ta

1g

1000mg20

mole

180g

1tablet

.250L

1L

moles.898x10 4

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 = .482from my calibration graph # 1 y = 0.1759X-0.0015

2.76M X

X0.1759

0.0015.482X

Don’t forget X10-4

the actual answer = 2.76X10-4 M

mg/Tablet4.248

1g

1000mg20

mole

180g

1tablet

.250L

1L

moles2.76x10 4

Mg Aspirin / Tablet table 24.2

Percent Aspirin / Tablet

Aspirin 67.02%X100et370mg/Tabl

blet248.4mg/Ta

Weight of entire tablet = 0.370g or 370mg