exp 4

Question 1

CHROMATOGRAPHY

• encompasses…?

Answer 1

• encompasses variety of techniques for separating individual compounds or compound types from a mixture

Question 2

SEPARATION in chromatography is affected by the ____ of the _____ of a given mixture between a ______ phase and a _____ phase

Answer 2

affinity

compounds

stationary

mobile

Question 3

2 types of CHROMATOGRAPHY

Answer 3

1. Adsorption
2. Partition

Question 4

ADSORPTION CHROMATOGRAPHY

• uses what 2 phases?
• separation is thru what process?

Answer 4

• uses a SOLID stationary phase and LIQUID mobile phase
• through SURFACE ADSORPTION PHENOMENA

Question 5

PARTITION CHROMATOGRAPHY

• uses what 2 phases?
• the 2 phases must be??
• separation is thru what process?

Answer 5

• uses LIQUID stationary phase & SOLID AND LIQUID or GAS mobile phase
• insoluble to each other
• through differences in the solubility of the sample in the stationary and mobile phases

Question 6

PROCESS of adsorption chromatography (3 steps)

Answer 6

1. mixture to be separated is placed (adsorbed) on solid stationary phase
2. the liquid mobile phase is allowed to flow
3. the individual components of the mixture to be separated will move at different rates = evident in separate regions (bands/spots) in the stationary phase

Question 7

The ____ of the _____ compound between the ____ phase and ___ phase is an _____ process

Answer 7

transfer

adsorbed

stationary

mobile

equilibrium

Question 8

ADSORPTION CHROMATOGRAPHY

• the extent of adsorption of a single component depends on… (3)

wherein the more _____ the compound to be separated is, the ______ it will be _____ on the surface of the ______ _____ phase

Answer 8

1. polarity of molecule
2. activity of adsorbent
3. polarity of liquid mobile phase

polar

more strongly

adsorbed

polar stationary

Question 9

ADSORPTION CHROMATOGRAPHY

the actual separation of the _____ in the mixture to be separated is dependent on….?

Answer 9

COMPONENTS - dependent on the

RELATIVE VALUES of the ADSORPTION-DESORPTION EQUILIBRIUM constant, K, for EACH of the components

Question 10

ADSORPTION CHROMATOGRAPHY

• most common example?
• ^ is a form of ________ adsorption chromatography that uses a ________ of _______ supported on a _______ as stationary phase
• most common adsorbent (2) and stationary phase (2) used

Answer 10

• Thin-layer chromatography
• solid-liquid adsorption
• thin layer of adsorbent
• flat surface
• alumina
• silica gel
• glass
• aluminum

Question 11

THIN-LAYER CHROMATOGRAPHY

importance (5)

Answer 11

1. useful in monitoring the progress of reactions
2. detecting intermediates in reactions
3. analyzing crude products/unknown mixtures
4. determining the number of components in a mixture
5. evaluating the efficiency of purification processes

Question 12

what PARTITION CHROMATOGRAPHY is similar to TLC?

• how is it different in terms of principle
• materials used?
• importance? (2)

Answer 12

Paper Chromatography

• uses liquid-liquid partition chromatography
• FILTER PAPER: made of highly purified cellulose, thus, absorbs and retains water molecules strongly
• used in rapid analysis of the components of a reaction mixture AND as a tentative means of identification

Question 13

What compound is an example of a HIGHLY PURIFIED CELLULOSE?

Answer 13

polyhydroxy

Question 14

PROCESS of PARTITION CHROMATOGRAPHY (3)

Answer 14

1. Small spots of mixture to be separated is placed at bottom of filter paper OR TLC plate
2. The liquid (solvent) mobile phase travels up the paper thru capillary action AT A RELATIVE RATE TO THAT OF THE SOLVENT FRONT
3. Bands/Spots also appear for each component of the mixture

Question 15

PARTITION CHROMATOGRAPHY

separation takes place due to the __________ of the _____ of the mixture for the _________ phase and ______ phase

wherein there is a _____ of ______ between the 2 phases, but those components that are _______ in the ______ phase will???

Answer 15

different affinities
components
polar stationary phase
nonpolar mobile phase

continuous exchange
solutes
more soluble
mobile

will spend more time in it and carried up faster

Question 16

what described the relative mobility of the compound?

and what formula does it use?

Answer 16

Retention Factor, Rf

= (distance travelled by compound from origin) / (distance travelled by solvent from origin)

where origin is midpoint of the original spot

Question 17

how to obtain distance traveled by a compound?

Answer 17

measure distance from origin to point of greater density of the spot corresponding to compound

Question 18

when can Rf be used for identification of a compound?

Answer 18

under a definite set of conditions (adsorbent, solvent, temperature, humidity)