Experiment 18 - Chromatography

Question 1

define polar molecule

Answer 1

a molecule that possesses a net dipole movement

Question 2

What is meant by “reverse phase” chromatography?

Answer 2

any situation in which the stationary phase is less polar than the mobile phase

Question 3

define non-polar molecule

Answer 3

a molecule that does not possess a net dipole movement

Question 4

define diffusion

Answer 4

the spreading, via random motions, of one substance through a space occupied by one or more substances

Question 5

define mixture

Answer 5

a combination of two or more substances in which the substances retain their identity

Question 6

How is Retention Factor calculated?

Answer 6

distance spot traveled/distance solvent travels from spotting line

Question 7

define solution

Answer 7

a homogenous mixture of two or more substances

Question 8

define chromatography

Answer 8

a laboratory technique that is used to separate components of a mixture by distributing components between two phases

Question 9

Why is the stationary phase in paper chromatography considered to be water?

Answer 9

water hydrogen bonds to the surface of the cellulose paper, forming a thin layer that functions as the stationary phase

Question 10

In order to gain good separations, what factor should be minimized?

Answer 10

sample amount

Question 11

define hydrogen bond

Answer 11

non-covalent interaction between a hydrogen atom (bonded to an electronegative atom) and another very electronegative atom to produce an unusually strong and directional dipole-dipole interaction

Question 12

What do higher retention volume measurements mean?

Answer 12

the component has a higher affinity for the stationary phase

Question 13

In order to gain good separations, what factor should be maximized?

Answer 13

migration differences