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Online Chemistry Labs | Learning Objectives

Background:

This experiment introduces students to thin layer chromatography as a means of studying intermolecular forces. After a discussion of the principles of TLC methodology, intermolecular forces between solvent and solute molecules, and the roles of stationary and mobile phases, the experiment turns to the specific cases of acetylsalicylic acid, acetaminophen, and caffeine for solutes and ethanol, ethylacetate, and cyclohexane for solvents. The student makes runs of each of the three solutes side-by-side in each of the solvents, recording the Rf factors for each case. Then an unknown of one of the three solutes is given to the student to investigate and identify. The student is asked to discuss observations in terms of intermolecular forces.

 TLC Elution

Learning Objectives:

  1. Become familiar with the methodology and practice of TLC.
  2. Learn how to the Rf factor by measuring spot movement on developed plates.
  3. Be able to compare Rf factors from runs with knowns with values for unknown runs.
  4. Be able to answer questions about the method and observed behavior of solute-solvent interactions.