1. Use the diagram showing a paper chromatography experiment to define the following terms:
(a) mobile phase
(b) stationary phase
(c) Rf value
2. Compare and explain the speed at which the following move up the paper in paper chromatography.
(a) Large molecules compared with small molecules.
(b) A polar solvent compared with a non-polar solvent.
3. An organic chemist is attempting to synthesise a fragrance compound by the following chemical reaction.
compound X + compound Y → fragrance compound
After one hour, a sample is removed and compared with pure samples of compounds X and Y using thin-layer chromatography. Which of the following chromatograms shows that the reaction has produced a pure sample of the fragrance compound?
4. Describe how chromatography can be used to identify the amino acids that make up a protein.
5. Label the parts A – F on the gas chromatography equipment below:
Labels
sample inlet
oven
gas (mobile phase)
detector
coil
chromatogram
6. In terms of gas liquid chromatography
(a) what is the mobile phase?
(b) what is the stationary phase?
(c) why is the injection port heated?
(d) explain what is meant by retention time.
7. Give 3 different uses of gas liquid chromatography.
8. (a) Which gases are usually used as carrier gases in gas chromatography?
(b) Explain why these particular gases are used.
9. If the stationary phase in gas chromatography is non-polar, how would the retention times of polar and non-polar samples in the column compare to each other?
10. A technician analyses a mixture of hydrocarbons using gas chromatography. She first calibrates the equipment using standard hydrocarbons. The retention times of these hydrocarbons are shown in the table.
| hydrocarbon | formula | retention time in minutes |
| methane | CH4 | 1.7 |
| ethane | C2H6 | 2.2 |
| propane | C3H8 | 3.5 |
| butane | C4H10 | 4.0 |
| pentane | C5H12 | 7.4 |
The technician then analyses the mixture of hydrocarbons. The recorder print out from this analysis is shown below.
(a) How does the recorder print out show that butane has the highest concentration?
(b) Use data in the table to draw a conclusion relating the formula of each hydrocarbon to its retention time.
