please try and answer from 9 thabk YOU f. Can chromatography be used to determin

Question

please try and answer from 9
thabk YOU

f. Can chromatography be used to determine how much of a component is in a mixture? How? · Use of GC in the calculation of % hexane and % toluene in the distillation experiment. . What is retention time? What does it tell us? Thin Layer Chromatography . What does a TLC plate look like before and after development? How are spots visualized on a developed plate? How is the developing solution chosen? . What is an Rf value? How is it calculated? Can it be greater than 1.0? . What is the purpose of the filter paper in the developing chamber? . How was the developing solvent chosen in these experiments? . Why was the TLC plate marked with pencil? . How could the appearance and number of spots be used to identify your unknown in these experiments? . You develop a plate that you had spotted a mixture of three components and see one blurred, spread-out "tail". What is the possible source of the poor separation? . You develop a plate that you had spotted a mixture of three components and see only two spots. What are possible sources for the third spot not showing up? 9. 10. General organic lab techniques: Watching the following videos one more time may be helpfiul. - Safety videos. Melting point determination, 2, Recrystallization,

Explanation / Answer

Before development all the spots will be at the same place. Whereas after the development the spots will move to different extent. If the component of the mixture is colored, then the spots can be observed by bare eyes without any further treatment. However if the compound is colorless then it is seen under UV light. Developing solution is chosen base on the polarity of the components.

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Rf = distance travelled by the compound / distance travelled by the solvent.

It can not be greater than 1.

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Filter paper absorb the liquid solvent and provide more surface area for evaporation and as a result the air surrounding the plane will be saturated with solvent vapor and evaporation rate will be less. In absence of the paper, solvent is evaporated more to saturate the air arround it.

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solvent is chosen depending on the polarity of the compounds.

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ink is a mixture of dyes and in presence of solvent it will seperate and as a result hamper the experiment.

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