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Chemistry LibreTexts

Chromatography - In-class Problem Set #1

Problem #1

After completing this problem, the student will be able to:

  1. Draw the idealized plot of the concentration of analyte in the stationary phase versus the concentration in the mobile phase as a function of increasing concentration of analyte injected into the chromatographic system.
  2. Recognize that in a real situation, the stationary phase will become saturated and the plot will deviate from ideality and exhibit Langmuir behavior
  3. Predict and justify what the chromatographic peaks will look like for Langmuir and anti-Langmuir behavior

Problem #2

After completing this problem, the student will be able to:

  1. Realize that a molecule dissolved in a liquid stationary phase moves by the process of diffusion.

Problem #3

After completing this problem, the student will be able to:

  1. Realize that a molecule dissolved in the mobile phase moves by two processes: (1) diffusion and (2) the physical motion of the flowing mobile phase.

Problem #4

After completing this problem, the student will be able to:

  1. Realize that starch, silica gel and alumina have hydroxyl groups on their surfaces and are therefore highly polar materials.
  2. Draw a plot of the distribution of enthalpies of adsorption for a molecule adsorbing onto silanol, disilanol and trisilanol groups.
  3. Recognize that the overall enthalpy of adsorption is the sum of the individual plots.
  4. Describe why the distribution of the enthalpy of adsorption is not symmetric.
  5. Predict the shape of the peak that would result for such a distribution of the enthalpy of adsorption and explain why this is not a favorable situation for chromatographic efficiency.