chromatography

Created by

gracey poo

Cards (22)

How many phases does chromatography use?
2
Name the two phases in chromatography.
mobile
stationary
What is the mobile phase?
Where the molecules can move. (a liquid or gas)
What is the stationary phase?
Where molecules can't move (solid or really thick liquid)
In chromatography the sample continuously moves between stationary and mobile phase (formulating equilibrium)
The mobile phase moves through the stationary phase, and anything dissolved in the mobile phase moves with it.
How quick a substance moves depends if it spends more time in the stationary phase or the mobile phase.
If a chemical spends more time in the mobile phase than stationary phase will it move further or not?
move further
A pure substance only has how many spots in a chromatography experiment?
1
What kind of paper is often used in chromatography?
filter paper
What kind of solvent is often used in chromatography?
ethanol or water
What stage is the paper in chromatography?
stationary
What phase is the solvent in chromatography?
mobile
What two things does time molecules spent in each phase depend on?
how soluble in the solvent they are
how attracted they are to the paper
Molecules with a higher solubility in the solvent and are less attracted to the paper will spend more time in which phase and how far will they be carried up?
Mobile phase
carried up further
The result of chromatography is called what?
a chromatogram
What is the rf value of a chemical?
The ratio between distance travelled by dissolved substance and distance travelled by solvent.
The further through the stationary phase a substance moves, the larger the what?
rf value
How do you calculate Rf?
distance travelled by substance / distance travelled by solvent
Distance travelled by substance is from the baseline to the spot of chemical.
Distance travelled by solvent is from the baseline to the solvent front.
To see if a substance if pure via chromatography you must run a pure sample alongside the unknown mixture.