chromatography and qualitative analysis

Question 1

chromatography

Answer 1

separating individual components from a mixture of substances

Question 2

stationary phase

Answer 2

doesn’t move, solid/ liquid support on a solid

Question 3

mobile phase

Answer 3

moves, solid/liquid

Question 4

uses of chromatography

Answer 4

drug analysis, forensic science, air samples

Question 5

TLC

Answer 5

thin later chromatography

quick, cheap analytical technique

Question 6

TLC plate

Answer 6

plastic sheet/ glass coated w/thin layer of adsorbent substance- silica

Question 7

limitations of chromatography

Answer 7

similar compounds have similar Rf values
finding the right solvent book through trail and error
experimental conditions Rf values need to match database values

Question 8

similarities bw paper and TLC

Answer 8

measure distance traveled as fraction of how far the solvent front has traveled
plate kept in chamber saturated w/solvent
useful for sep pigments

Question 9

stationary phase of TLC

Answer 9

adsorbent- silica

Question 10

why is it common to run TLC of sample alongside pure samples of compounds that may be present?

Answer 10

easy to identify amino acid in unknown sample visually w/out needing o calculate any Rf values

Question 11

what does a high affinity for solvent mean

Answer 11

further distance traveled by pigment

Question 12

why are there diff Rf value for different substances

Answer 12

each sub has a diff affinity for certain solvent

different adsorption strengths to silica surface

Question 13

retention time

Answer 13

time taken for a substance to pass through the column

Question 14

adsorption

Answer 14

solid silica holds diff sub in mixture onto its surface

Question 15

Rf

Answer 15

retention factor

distance traveled by component/ distance traveled by solvent

Question 16

why does separation take place?

Answer 16

substances in mixture have diff affinity for the stationary and mobile phase, the more a sub sticks to stationary phase the less distance it travels

Question 17

draw and annotate steps of TLC

Answer 17

.

Question 18

purpose of watch glass

Answer 18

prevents solvent from evaporating away

Question 19

purpose of spraying chromatography with locating agents and heating with hair dryer

Answer 19

to show to position of invisible spots

Question 20

use of gas chromatography

Answer 20

separating and identifying volatile compounds in a mixture

Question 21

GC stationary phase

Answer 21

high bp liquid adsorbde

Question 22

alkene

Answer 22

add bromine water

bromine water delcolourises from orange to colourless

Question 23

haloalkane

Answer 23

add sliver nitrate and ethanol and warm in w.bath(50)
chloroalkane- white ppt
bromoalkane-cream ppt
iodoalkane- yellow ppt

Question 24

carbonyl 2,4-DNP

Answer 24

orange ppt

Question 25

aldehyde

Answer 25

tollen’s reagent and warm

silver mirror

Question 26

primary and secondary alcohol and aldehyde

Answer 26

acidifed potssium dihromate(VI) nd warm in water bath

colour change from orange to green