Goals Answer all questions
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Instructions Use the chromatograms to answer the questions. Goals Answer all questions
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| In the following examples, 4 different marker pigments were separated on strips of chromatography paper.
The markers were black, blue, brown, and yellow.
A starting line was drawn with each marker on a separate strip of chromatography paper,
and each strip was placed in a glass jar with a small amount of solvent.
The solvent wicks up the paper and moves the pigments along with it.
The solvent in each of these examples is water, which is polar.
![]() The results of the 4 different marker chromatography experiments are shown in the image above.
From left to right, the markers are black, blue, brown, and yellow.
Because water is a polar solvent, what can we tell about the different marker pigments?
Which markers contained only one pigment?
Which markers contained a mixture of pigments?
Rank the pigments from most polar to least polar.
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Goals Watch the chromatography experiment
| In the following chromatography experiment,
kale leaves were rubbed on the base of a strip of chromatography paper.
The strip was then placed in a glass jar with a non-polar solvent, petroleum ether.
Watch the video below to see the experiment in action.
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Goals Answer all questions
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| The image below shows results of a chromatography experiment using kale leaves,
just like the video you just saw.
The four plant pigments shown in the chromatogram are beta-carotene (yellow orange),
xanthophyll (lighter yellow), chlorophyll a (bright green), and chlorophyll b (olive green).
Use the chromatogram to answer the following questions.
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Goals Answer all questions
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Goals Answer all the questions
| In paper chromatography, you can calculate the different retention factors
(abbreviated Rf) for each pigment.
The Rf value for each substance is the distance the substance traveled
divided by the distance the solvent traveled.
Rf = distance substance traveled / distance solvent traveled ![]() What is the distance the solvent traveled?
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Goals Answer all the questions
| Not all chromatograms have clear, compact bands like in the previous example.
Quite often bands will have broad, smeared sections.
How are Rf values calculated from these bands?
Although there are several way to calculate Rf values for smeared bands, one of the best ways is to determine the center of each band. To do this, you need to know the highest and lowest points of the band. The center of the band is then calculated by the following equation: Center = [ (highest point - lowest point) / 2 ] + lowest point ![]() The band in the image above extends from 5 to 7.
What is the value of "highest point" for this equation?
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Goals Answer all the questions.
| Now let's use a real chromatogram to calculate Rf values.
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Instructions You have completed the lesson. You may scroll up to review the lesson. |