Lesson 5: Chromotography Flashcards
What is chromotography?
A separation technique separates substances in mixture due to different solubilities.
What will happen if a dye is less soluble than others?
- It won’t travel as far up the filter paper.
What will happen if a dye isn’t soluble in the solvent?
- It won’t travel up the filter paper.
Why is the baseline drawn in pencil?
- Pencil is insoluble: won’t smudge or run up.
Why does the baseline have to be above the solvent line?
- To ensure the dyes don’t dissolve immesdiately into solvent.
What is the stationary phase?
- Filter paper
What is the mobile phase?
- Solvent
What is the solvent front?
- Solvent front is the furthest distance travelled by the solvent .
Why do inks separate?
- Difference in solubility
- Difference in molecular mass.
Causes them to move at different rates
How do you calculate Rf value?
Distance moved by substance/ distance moved by solvent.
What is chromotography used for?
- Chromatography can be used to separate mixtures and can give
information to help identify substances.
What does separation of compounds in a mixture depend on in paper chromotography?
- Separation depends on the
distribution/ attraction of substances between the phases (mobile/ stationary phases.) - Ie. compound spends more time in mobile phase (solvent) moves higher up filter paper.
What would the chromatogram of a pure substance undergone paper chromotography look like?
- It will have a single spot (no matter what solvent was used for the chromatography.)
If i use ethanol as a solvent for the chromotography of Mixture A and then use water for Mixture A, will the Rf vales for compounds on the chromatogram’s be the same?
- No.
- Compounds have different Rf values in different solvents.
How do the compounds in a mixture separate in chromotography?
- They may separate into different spots depending on the solvent used.
