Chemistry- Chromatography UPDATED
ACTUAL Exam Questions and CORRECT
Answers
What are the two types of chromatography? - CORRECT ANSWER - thin layer
chromatography (TLC)
gas chromatography (GC)
What is TLC used to separate? - CORRECT ANSWER - mixtures of organic molecules
What does the TLC separation work by? - CORRECT ANSWER - adsorption
What is the stationary phase in tlc? - CORRECT ANSWER - a polar solid that does not
move
What is the mobile phase in TLC? - CORRECT ANSWER - an organic liquid solvent that
carries the compounds
Solvent - CORRECT ANSWER - the substance that dissolves the solute
In TLC, the more polar the compound, the ...... the adsorption? - CORRECT ANSWER -
stronger
In TLC, the stronger the adsorption, the ..... the Rf? - CORRECT ANSWER - lower
In TLC, more hydrogen bonding means more .....? - CORRECT ANSWER - adsorption
In TLC, more adsorption means the substance will run up the plate ....? - CORRECT
ANSWER - less
, What are measurements taken from TLC used to do? - CORRECT ANSWER - identify
present compounds
What measurements are taken in TLC to calculate Rf? - CORRECT ANSWER - distance
travelled by solvent
distance travelled by individual spots
What do individual spots in the TLC normally represent? - CORRECT ANSWER -a
single compound
Do individual spots on a TLC always represent a single compound? - CORRECT
ANSWER - no, can be multiple compounds with similar/same Rf
What is the formula to calculate Rf? - CORRECT ANSWER - Rf = distance travelled by
the dye / distance travelled by the solvent
In TLC will the Rf value be different for different compounds if done under the same conditions?
- CORRECT ANSWER - yes
What are the limitations of TLC? - CORRECT ANSWER - Similar compounds have
similar Rf values (due to similar polarities b/c of same or similar functional groups)
Unknown samples have no reference sample for comparison
Can be difficult to find a solvent to separate all components
In TLC, which of methylbenzene and phenol would have the highest Rf and why? - CORRECT
ANSWER - methylbenzene- phenol has hydrogen bonding so would have more
adsorption, methylbenzene has IDDs and no hydrogen bonding so will have less adsorption so
will run up more so will have a greater Rf
ACTUAL Exam Questions and CORRECT
Answers
What are the two types of chromatography? - CORRECT ANSWER - thin layer
chromatography (TLC)
gas chromatography (GC)
What is TLC used to separate? - CORRECT ANSWER - mixtures of organic molecules
What does the TLC separation work by? - CORRECT ANSWER - adsorption
What is the stationary phase in tlc? - CORRECT ANSWER - a polar solid that does not
move
What is the mobile phase in TLC? - CORRECT ANSWER - an organic liquid solvent that
carries the compounds
Solvent - CORRECT ANSWER - the substance that dissolves the solute
In TLC, the more polar the compound, the ...... the adsorption? - CORRECT ANSWER -
stronger
In TLC, the stronger the adsorption, the ..... the Rf? - CORRECT ANSWER - lower
In TLC, more hydrogen bonding means more .....? - CORRECT ANSWER - adsorption
In TLC, more adsorption means the substance will run up the plate ....? - CORRECT
ANSWER - less
, What are measurements taken from TLC used to do? - CORRECT ANSWER - identify
present compounds
What measurements are taken in TLC to calculate Rf? - CORRECT ANSWER - distance
travelled by solvent
distance travelled by individual spots
What do individual spots in the TLC normally represent? - CORRECT ANSWER -a
single compound
Do individual spots on a TLC always represent a single compound? - CORRECT
ANSWER - no, can be multiple compounds with similar/same Rf
What is the formula to calculate Rf? - CORRECT ANSWER - Rf = distance travelled by
the dye / distance travelled by the solvent
In TLC will the Rf value be different for different compounds if done under the same conditions?
- CORRECT ANSWER - yes
What are the limitations of TLC? - CORRECT ANSWER - Similar compounds have
similar Rf values (due to similar polarities b/c of same or similar functional groups)
Unknown samples have no reference sample for comparison
Can be difficult to find a solvent to separate all components
In TLC, which of methylbenzene and phenol would have the highest Rf and why? - CORRECT
ANSWER - methylbenzene- phenol has hydrogen bonding so would have more
adsorption, methylbenzene has IDDs and no hydrogen bonding so will have less adsorption so
will run up more so will have a greater Rf
