Chromatography
This practical lesson covers:
- How paper chromatography can be used to separate and tell the difference between coloured substances
Investigating paper chromatography
Aim
To investigate how paper chromatography can be used to separate and tell the difference between coloured substances, including the calculation of Rf values.
Background information
Paper chromatography is a method used to separate coloured substances. In this practical, you will apply a small sample of a mixture, such as ink or plant extract, near the bottom of a strip of chromatography paper. When the lower end of the paper is immersed in the solvent, the solvent will rise up the paper. As it moves, the different substances in the sample will separate. By observing the distinct bands that form, the composition of the mixture can be analysed.
What is the purpose of paper chromatography?
to separate and differentiate between coloured substances
to measure the distance traveled by the solvent
to investigate how paper is made
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What should be done if the water solvent does not travel three quarters of the way up the paper?
remove the paper immediately
calculate Rf values without waiting
disturb the beaker to speed up the process
wait longer for the solvent to travel
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What is the purpose of drawing another pencil line on the dry part of the paper?
to indicate the end of the experiment
to calculate Rf values
to measure the distance traveled by the solvent
to mark the solvent front line
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What is the significance of the solvent front line in paper chromatography?
It marks the end of the experiment
It helps calculate Rf values
It indicates the starting point for the solvent
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