Interpreting Chromatograms Flashcards
In paper chromatography, what is the piece of paper called?
A chromatogram.
What do you do if you have chemicals in your mixture that are colourless?
Spray the chromatogram with a chemical called a locating agent to show where the spots are.
What is an Rf value?
The ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent.
What is the formula for Rf values?
Rf = distance travelled by solute ÷ distance travelled by solvent
How do you find the distance travelled by the solute?
Measure from the baseline to the centre of the spot.
What is chromatography often used for?
To see if a certain substance is present in a mixture.
How can you check if a certain substance is in a mixture, using chromatography?
Run a pure sample of a substance you think might be in the mixture and compare the Rf values.
What is the name given to pure samples that are run next to a mixture?
Standard reference materials (SRMs).
What two features of SRMs are controlled?
Concentrations and purities.
How can you tell a pure substance from a mixture, in terms of spots?
A pure substance won’t separate, and will move as one blob, whereas a mixture will give multiple blobs.
