Chromatography

Question 1

what are the two key phases in chromatography

Answer 1

mobile and stationary phase

Question 2

mobile phase

Answer 2

a liquid or a gas that carries the mixture through a system

Question 3

stationary phase

Answer 3

a solid or a solid-supported liquid that does not move with the mobile phase

Question 4

how does solubility of components affect separation in chromotography

Answer 4

the mobile phase moves mixture components at varying speeds, depending on their solubility. the easier the component is to dissolve, the fast they’ll move

Question 5

how does adsorption affect chromotography

Answer 5

the stationary phase holds onto compounds differently through adsorption. components that are adsorbwed more strongly move slower.

Question 6

what are the two types of chromotography you need to know abouut

Answer 6

1. thin layer chromotography
2. gas chromotography

Question 7

what is the process of thin-layer chromotography

Answer 7

1. the stationary phase (the TLC plate, commonly made from silica gel or alumina) is spread thinly on glass/metal
2. small amount of the mixture to be analysed is applied close on the TLC plate’s bottom edge
3. the plate is placed upright in a sealed container with a small amount of solvent in the bottom
4. the solvent moves up the plate by capillary action, at various rates
5. once the solvent has nearly reached the top, the plate is removed and the locations of the separate components are marked

Question 8

how to calculate Rf vaues

Answer 8

Rf = distance travelled by spot / distance travelled by solvent

Question 9

how does the Rf valye help to identify components

Answer 9

by comparing the Rf values of that those that are known substances, under the same chromatographic conditions

Question 10

what is the process of gas chromatography

Answer 10

1. a liquid sample is vaporised in a heat chamber
2. an inert carrier gas then transports the vaporised sample through a chromatographic column containing the stationary phase