Experiment 7

Question 1

What kind of partitioning technique is column chromatography?

Answer 1

solid-liquid partitioning techinique

Question 2

What is the mobile phase in chromatography column?

Answer 2

carries the sample through the stationary phase which is packed inside a glass column

Question 3

What are the differences between the mobile phase in column chromatography and TLC?

Answer 3

• eluent will descend down the packed, solid column
• in TLC a single solvent is used to separate the components of a mixture and in column it is common to use a mixture of solvents in order to achieve separation

Question 4

What was the absorbent used in the laboratory?

Answer 4

alumina (Al2O3)

Question 5

What is the simple break down of steps for running a column chromatography?

Answer 5

1. sample mixture is added to an appropriate eluent. The solution consisting of both is added to the column.
2. as the solution moves through the column the compounds will interact with the stationary phase.
3. if the compounds have a difference in attraction for the stationary phase then they move at diff. rates down the packed column.

Question 6

how does polarity relate to the movement of compounds down a chromatographic column?

Answer 6

• the more polar the compound, the slower it will travel down the column.
• the less polar the compound, the faster it will travel down the column.

Question 7

What are some typical problems associated with running a column chromatography?

Answer 7

• non-horizontal bands
• streaming
• cracking

Question 8

What is channeling?

Answer 8

occurs if there are any cracks or irregularities in the absorbent surface or any irregularities caused by air bubbles in the packing.

Question 9

What causes the process of cracking with a chromatographic column?

Answer 9

the formation of vapor creates bubbles, which forces a separation of the column packing

Question 10

What are the two ways to try to avoid problems when running a column chromatography?

Answer 10

-Use a support base (generally sand is used)
- columns should be evenly packed and free of irregularities, air bubbles, and gaps
(important that the leading edge, or front, of every band to be horizontal or perpendicular to the long axis of the column)

Question 11

What are the five different interactions found between the eluent and absorbent studied in lab?

Answer 11

coordination, dipole-dipole, hydrogen bonding, salt formation, and van der waals

Question 12

What is the strength of the interactions in order?

Answer 12

salt formation > coordination > hydrogen bonding > dipole-dipole > Van der Waals

Question 13

objective

Answer 13

to prepare an absorption chromatography column and then use it to separate a mixture of ferrocene from acetylferrocene and find the percent recovery