Separation techniques Flashcards
What is the purpose of chromatography?
1) Separate a mixture of soluble dyes
2) Check the purity of a sample
3) Calculate Rf
How do you tell if a substance is pure?
1 dot = pure
>1 dot = impure
what is the mobile phase?
the one that moves (solvent)
what is the stationary phase?
the one that doesn’t move (paper)
Describe the method for chromatography
1) Draw baseline in pencil
2) Draw sample on baseline
3) Place chromatogram into the solvent
4) Let it run
5) Mark the solvent front
Why do we use pencils to draw the baseline?
Because it’s insoluble
The amount of time the molecules spend in each phase depends on:
~ the solubility
~ an attraction to the phases
the higher the solubility…
the less attracted to the paper so they spend more time in the mobile phase + travel further up the paper (they want to get away from the paper)
the lower the solubility…
the more attracted to the paper so they spend more time in the stationary phase + stay at the bottom of the paper (they like the paper)
How do you calculate the Rf?
Distance moved by compound (spot) / distance moved by solvent (SF to baseline)
Extra info about Rf
doesn’t need units and is always lower than 1
What is the purpose of distillation?
to separate a mixture of liquids
what is simple distillation?
when the liquids have very different boiling points fractional distillation is the opposite
what are the key pieces of equipment for simple distillation?
- Bunsen burner
- thermometer
- anti-bumping granules (stops it from over boiling, allows it to boil smoothly)
- bucket of ice
overview of the method for simple distillation:
1) heat the liquid until it turns into a gas (evaporation)
2) cool gas into a liquid (condensation)
