Tlc Chem 121

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Abstract

In order to experiment with distinct components of a mixture, they must be first separated so they can be observed individually. This is accomplished in this lab by the technique called thin layer chromatography (TLC). TLC involves a stationary phase, which the TLC plates as well as a mobile phase, which could be one of two solvents used: ethanol-acetone for TLC. Dyes in a sample separate consequently because of their unique polarities. As a result, nonpolar substances travel further than polar substances in this process. The separation of a mixture into its components by TLC transpires because the distinctive components of a mixture interact to different extents with the stationary and mobile phases.

It was determined that Unknown #7 contains Methylene blue, Methyl violet, Basic fuchsin, and Methyl red. We determined that Unknown #3 contains Methylene blue, Rhodamine B, Methyl violet, and Clayton Yellow (or Methyl red). The reason that the yellow or red is stated is because there were no Rf values and the colors had to be compared to the pictures that were taken of the other TLC plates on our iPhones.

Rfdye 1=L1Ls

Use millimeters when measuring the distances of the dyes and the solvent front. You should calculate the Rf for each dye. When measuring the distance traveled, measure to from the origin to the center of the spot (See figure 3). Prelab Exercise

1. Using a ruler (measuring in millimeters), determine the Rf value for each of the dyes in on the following TLC plate.

solvent front

origin

Rf (dye 1) = 28/68=.41176| Rf (dye 4) = 43/68= .63235|
Rf (dye 2) = 52/68= .76471| Rf (dye 5) = 17/68= .25|
Rf (dye 3) = 8/68= .11765| Rf (dye 6) = 63/68= .92647|

2. We can see that dye #3 travelled the least distance during the development process. As a result the Rf value for dye #3 is the smallest of the six. What would cause the dye to travel less than the other dyes? * see answer on #3

3. We can see that dye #6 travelled the farthest distance during the development process. As a result the Rf value for dye #6 is the largest of the six. What would cause the dye to travel farther than the other dyes? How fast the compounds get carried up the plate depends on two things: 1. How soluble the compound is in the solvent. This will depend on how much attraction there is between the molecules of the compound and those of the solvent. 2. How much the compound sticks to the stationary phase - the silica gel, for example. This will depend on how much attraction there is between the molecules of the compound and the silica gel. Data Table

solvent: ethanol
| Methyl Violet| Clayton Yellow| Rhodamine B| Methylene Blue| Methyl Red| Basic Fuchsin| L dye| | | | | | |
L solvent| | | | | | |
Rf| | | | | | |

solvent: acetone
| Methyl Violet| Clayton Yellow| Rhodamine B| Methylene Blue| Methyl Red| Basic Fuchsin| L dye| | | | | | |
L solvent| | | | | | |
Rf| | | | | | |

solvent: 60% acetone/40% ethanol
| Methyl Violet| Clayton Yellow| Rhodamine B| Methylene Blue| Methyl Red| Basic Fuchsin| L dye| | | | | | |
L solvent| | | | | | |
Rf| | | | | | |

Unknown #_______
| Spot #1| Spot #2| Spot #3| Spot #4| Spot #5| Spot #6| L dye (1)| | | | | | |
L dye (2)| | | | | | |
L solvent| | | | | | |
Rf (1)| | | | | | |
Rf (2)| | | | | | |

Unknown #_______
| Spot #1| Spot #2| Spot #3| Spot #4| Spot #5| Spot #6| L dye (1)| | | | | | |
L dye (2)| | | | | | |
L solvent| | | | | | |
Rf (1)| | | | | | |
Rf (2)| | | | | | |

Identity of dyes in each unknown:

Unknown #_____ contains:

Unknown #_____ contains:

Notes for Data Table

You will fill out a table for each of the three solvent systems. Determine which solvent system is the best at separating all six of the dyes. Use this...
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