chromotography Flashcards
(14 cards)
Step 1: take a piece of…
filter paper
Step 2: draw a pencil line towards the bottom. This is known as the…
‘baseline’
Step 3: Add the _________ of ink to the…
sample/ baseline
Step 4: Find a beaker and fill it with a…
shallow amount of solvent (water or ethanol)
Step 5: Place the paper into the _________ BUT
solvent, the baseline must not be submerged
Step 6: As the paper absorbs the solvent, the ink will…
run with it as it dissolves into the mobile phase.
Why do the dyes separate?
Each component travels up the paper at different rates and separate out, which tells us that they are all different substances.
If any of the dyes aren’t soluble they will…
stay on the baseline.
What do we call the final spots on the paper that are left?
a chromatogram
Mobile phase =
substance that molecules can move in (usually a liquid or gas)
Stationary phase =
substance/material that the molecules can’t move in (the filter paper)
Why does each ink move at different rates? Refer to stationary and mobile phase:
The different inks alternate between the mobile phase and stationary phase, but how much time they spend in each phase overall results in different rates at which they move.
this depends on the properties of the substance.
How can scientists use a chromatogram to identify a substance?
They can figure out it’s Rf value, whilst considering the different mobile and stationary phases employed, since the Rf value changes according to the properties of a substance.
Rf value =
the distance travelled by a substance/ the distance travelled by the solvent
