Why should the line at the bottom of the chromatography paper not be drawn in pen?
As the pigments in the pen would separate
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How is the chromatography paper attached to the test tube containing the solvent?
Using a drawing pin attached to a bung.
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Why should there be a bung in the test tube?
So that the atmosphere in the beaker remains saturated with solvent vapour, stopping the solvent from evaporating as it rises up the paper.
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What type of ruler should be used to measure the distances of the solvent & pigments?
A transparent plastic ruler, starting from the 0 end.
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How is the Rf value calculated?
Distance travelled by pigment/Distance travelled by solvent
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What is the independent variable?
The leaf that pigment is taken from
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What is the dependent variable?
Rf values of the pigments in each leaf.
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How is the leaf extract prepared?
Leaves are ground up using a pestle & mortar and soaked in a fast evaporating solvent (e.g. propanone).
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Give one other reason for adding propanone (acetone)
Dissolves the phospholipid membrane so that more pigment is released.
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What is a suitable mixture of solvents for the mobile phase? (3 solvents)
Cyclohexane, propanone (acetone) and petroleum ether.
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Leaves from which types of plant could be compared? (2 types)
Shade - tolerant and plants growing in sunlight.
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What are the controlled variables?
Part of spot to which is measured from the solvent line (e.g. top of spots), mixture of solvents, concentrations of solvents, stationary phase (e.g. paper), approximate amount of pigment placed on plate.
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How are the plant pigments in each leaf deduced?
Compare the Rf values to a database of known Rf values for different plant pigments.
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What number should Rf values always be below?
1
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Other cards in this set
Card 2
Front
How is the chromatography paper attached to the test tube containing the solvent?
Back
Using a drawing pin attached to a bung.
Card 3
Front
Why should there be a bung in the test tube?
Back
Card 4
Front
What type of ruler should be used to measure the distances of the solvent & pigments?
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