15E.1

Question 1

what is chromatography used for

Answer 1

1. to separate the mixture into components
2. to identify the components of the mixture by considering how far they have travelled up the paper
3. to check if an organic compound is pure or not by following the two things above

Question 2

what do you need to set up a chromatography experiment

Answer 2

1. a container (made out of glass) it could be a beaker or a rectangular tank with a lid
2. paper. we can use filter paper or kitchen towel but using a chromatography paper gives better results. also we need a method to support the paper in the container
3. solvent. water can work, but in most situations it is a a mixture of organic compounds, that are chosen to fit the characteristics of the of the components of the mixture

Question 3

why do we use a lid in chromatography

Answer 3

the prevent the evaporation of the solvent

Question 4

how do you carry out a chromatography

Answer 4

the mixture is spotted onto the paper a short distance away from the edge ( often spots of known substances are spotted separately at the same level as the mixture ) then a small amount of the chosen solvent is added to the container, and the paper is inserted and suitably supported, then the lid is replaced and the apparatus is left till the solvent front reaches almost the end of the paper, the paper is removed and the solvent front is marked and then the paper will be left to dry

Question 5

what is the chromatogram

Answer 5

the dried paper used in chromatography

Question 6

usually in the chromatogram the spots are

Answer 6

elongated and hard to find there centers

Question 7

chromatography depends on the use of

Answer 7

1. the stationary phase
2. the mobile phase

Question 8

what is the stationary phase in chromatography

Answer 8

the liquid or solid that does not move

Question 9

what is the mobile phase in chromatography

Answer 9

the liquid that moves through the stationary phase and transports the components

Question 10

components who don’t travel very far up the paper are

Answer 10

strongly attracted to the stationary phase but weekly attracted to the mobile phase

Question 11

components who travel very far up the paper are

Answer 11

strongly attracted to the mobile phase and weekly attracted to the stationary phase

Question 12

in paper chromatography the mobile phase is

Answer 12

the solvent

Question 13

in paper chromatography the stationary phase is

Answer 13

the water that is trapped in the fibers of the chromatography paper

Question 14

how do we get coloured components when doing paper chromatography on organic substances

Answer 14

1. using ultraviolet radiation
2. by spraying with a chemical regent that will react with components to from a coloured product

Question 15

what is the difference between thin-layer chromatography (TLC) and paper chromatography

Answer 15

in TLC is the same as paper chromatography just the paper is replaced by a sheet of glass or plastic coated with a thin layer of solid such as silica or alumina

Question 16

how do you calculate the Rf (retardation factor) value

Answer 16

distance travelled by component / distance travelled by solvent (no units since ratio)

Question 17

each component in chromatography will have

Answer 17

its own Rf value

Question 18

the Rf value depends on

Answer 18

solvent used and other factors (the paper (stationary phase) )

Question 19

can we always use Rf to identify components

Answer 19

yes from the table, but in different solvents components will have different Rf

Question 20

the distance moved by the component is

Answer 20

the distance measured between the baseline and center of the component

Question 21

the distance moved by the solvent is

Answer 21

the distance measured between the baseline and the solvent front

Question 22

why do we put known substances beside the mixture

Answer 22

to see if the mixture has any of those substances

Question 23

how does column chromatography work

Answer 23

alumina or silica are packed into a tube ( a burette is suitable) and are soaked with the solvent, the mixture is then places on top of the silica/alumina and then more solvent is added on top , then the tap is opened and the solvent will drip through the tip and the mixture begins to move down the top and sperate, then more solvent is added at the top of the burette and eventually on component leaves the column and is collected in a container (we can do the same thing for all the other components)

Question 24

in column chromatography the stationary point is

Answer 24

the alumina or silica

Question 25

in column chromatography the mobile phase is

Answer 25

the solvent

Question 26

what is the advantage of column chromatography

Answer 26

larger quantities of material can be separated