Cliffs AP Chemistry, 3rd Edition

Analysis:

1. Using a cm rule, determine the length of the solvent front.
   The chromatogram indicates the solvent traveled 15.0 cm.


2. Measure the distance that each component traveled, measuring from the middle of the spot
   to the point of application and determine Rf.

Dye Rf

FDC* Blue 1

.

R.

15 0

13 9

f=

= 0.927

FDC Blue 2

.

R.

15 0

33

f=

= 0.22

FDC Red 3

.

R.

15 0

10

f=

= 0.067

FDC Yellow 5 **

.

R.

15 0

79

f=

= 0.52

Unknown Mixture 1 at 3.4 cm Rf= 0.23

1 at 7.8 cm Rf= 0.53

*FDC — Food, Drug and Cosmetic Act

**Causes hyperactivity in some children

3. What conclusions can you make regarding the unknown mixture?
   The unknown mixture clearly shows that it was composed of FDC Blue 2 and FDC
   Yellow 5. Since blue dye mixed with yellow dye gives green dye, the color of the un-
   known sample, this further supports the conclusion.

Part III: AP Chemistry Laboratory Experiments