Chromatography RP

Question 1

Method

Answer 1

1. get chromatography paper and draw a line in pencil 1.5 cm from the bottom
2. mark two (or number of substances you are testing) crosses on the line, in pencil
3. place a spot of each substance on a different cross on the line
4. hang piece of paper in a beaker and add a small amount of solvent, e.g. ethanol until it reaches the paper. Make sure it doesn’t go past the line drawn in pencil
5. allow the solvent to rise up the paper
6. measure the distance of how far the solvent has moved, aswell as each spot on the chromatography paper
7. calculate the Rf values of each spot ( distance moved by spot/distance moved by solvent) in centimetres using a ruler
8. If Rf values match, then the substances are the same

Question 2

what would increase the distance between two spots that are close together

Answer 2

• allowing the solvent front to travel further
• using a different solvent

Question 3

What would produce a smaller Rf value if solvent and paper are both changed

Answer 3

A substance that is less soluble and has a higher attraction to the paper

Question 4

Why is the starting line drawn in pencil

Answer 4

Pencil is insoluble and won’t move in the mobile phase

Question 5

what is the mobile phase

Answer 5

The solvent - the solvent moves

Question 6

what is the stationary phase

Answer 6

the paper - it doesn’t move

Question 7

what can affect the distance moved by the substance

Answer 7

• attraction to the paper in the stationary phase
• solubility of substance in mobile phase