3.5. Chromatography

Question 1

What is the basic idea behind chromatography?

Answer 1

A mobile and a stationary phase and how long molecules spend in each

Question 2

Position of equlibrium?

Answer 2

If a substance is more attracted to the mobile phase the position of equlibrium lies towards that and vice versa.

Question 3

How does chromatography separate substances?

Answer 3

Chromatography separates substances by making use of differences in their

• polarity
• • molecular size

Question 4

What decides how far/fast the substances travels during chromatography

Answer 4

The relative affinity for the mobile phase and the stationary phase

Question 5

What are the mobile and stationary phases in paper chromatography?

Answer 5

Stationary: Wet Paper

Mobile: A suitable solvent

Question 6

Why must we consider the molecular size in chromatography?

Answer 6

Larger molecules will travel through the mobile phase more slowly

Question 7

What is the mobile phase in GLC?

(gas-liquid chromatography)

Answer 7

An inert gas (He or N₂ )

This is so it doesn’t react with any substances

Question 8

What are the 2 axes on a GLC result?

Answer 8

X: Retention time

Y: Abundance

Question 9

Give an advantage of TLC over Paper Chromatography

Answer 9

The mobile phase moves

• more quickly through the stationary phase
• • more evenly through the stationary phase

Question 10

What is the basic set up for Thin Layer Chromatography ( TLC) ?

Answer 10

Question 11

What is meant by the retention factor ( R_f ) in paper chromatography and TLC?

Answer 11