Thin Layer Chromatography Chem 237 – Flashcards
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A student is comparing two samples of crystalline organic solids. A TLC analysis shows a single spot for each sample and the co-spot with the same Rf value. Which of the following would provide the most conclusive evidence that the two samples are the same compound?
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Perform a mixture melting point.
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The active ingredients in an over the counter analgesic pill were separated by TLC on silica, using a solvent system of hexane and ethyl acetate. Identify where the waste generated by this process should go. Drag and drop the chemical wastes generated in this reaction into the appropriate container.
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Hexane, ethyl acetate, and acetone should go in the non-halogenated organic waste container. TLC plates and spotting capillaries should go to the solid waste container.
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A TLC plate was run in 1:1, hexane:ethyl acetate, but when developed the plate only showed baseline spots. What change could be made to get the spot(s) to move further up the plate?
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spot a new plate and run in 1:4, hexane:ethyl acetate
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The retention factor, or Rf, is a number that describes the position of a spot on a chromatography plate relative to the position of the solvent on the chromatography plate. What are the minimum and maximum values of Rf?
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Min: 0
Max: 1
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Silica is toxic
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False
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Hexane is flammable
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True
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Ethyl Acetate is flammable
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True
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Acetone is flammable
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True
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It is acceptable to handle TLC plates with bare hands.
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False
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An over the counter headache pill was crushed, extracted into ethanol / dichloromethane, and then analyzed by TLC on silica using ethyl acetate as an eluent. The pill was shown to contain: acetaminophen, aspirin, and ibuprofen.
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Highest Rf
Ibuprofen (most nonpolar)
aspirin
acetaminophen (most polar)
Lowest Rf
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What is the major underlying principle of chromatography?
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Separation will be achieved if one component adheres to the stationary phase more than the other component does.
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In regard to the TLC plate you will be using in lab, which statement is true?
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The stationary phase is more polar than the mobile phase.
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For a successful TLC experiment, you need to pay attention to the details. From the list of instructions and tips below, select the detail that is NOT important to a TLC experiment.
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Closely monitor the temperature of the solvent in the chamber.
