paper chromatography

Question 1

what is chromatography used for

Answer 1

chromatography is used to separate substances in a mixture and identify them

Question 2

what are the two phases in chromatography

Answer 2

• Mobile phase – Where molecules can move (e.g., the solvent in paper chromatography).
• Stationary phase – Where molecules cannot move (e.g., the paper in paper chromatography).

Question 3

how does paper chromatography work

Answer 3

• The solvent moves up the paper, carrying the substances in the mixture.
• The amount of time a chemical spends dissolved in the solvent vs. stuck to the paper determines how far it moves.

Question 4

what affects how far a solvent moves

Answer 4

• Solubility: More soluble substances move further up the paper.
• Attraction to the paper: The more a substance sticks to the paper, the less it moves.

Question 5

what is a chromatogram

Answer 5

A chromatogram is the result of a chromatography experiment, showing the separated substances as spots on the paper.

Question 6

what is the solvent front

Answer 6

The solvent front is the furthest point reached by the solvent during chromatography.

Question 7

how can you tell if a substance is pure using chromatography

Answer 7

If a substance produces only one spot in multiple different solvents, it is pure.

Question 8

what is the Rf value

Answer 8

The Rf value is the ratio of how far a substance moves compared to how far the solvent moves.

Question 9

what is the formula for finding the Rf value

Answer 9

Rf = Distance moved by substance (B) ÷ Distance moved by solvent (A)

Question 10

how can chromatography be used to identify substances in a mixture

Answer 10

• A pure sample of a known substance is run next to the mixture.
• If a spot in the mixture matches the reference substance (same Rf value in multiple solvents), they are likely the same.