Unit 3 Chemistry
Name:_______________
Chromatography Test
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1. What term is used to describe the sticking of particles to the surface of the stationary phase in
chromatography?
A.
B.
C.
D.
Desorption
Adsorption
Retention
Retardation
2. A mixture is separated by thin layer chromatography. Compared with the other components
of the mixture, the component with the lowest Rf value must be:
A.
B.
C.
D.
the most strongly attracted to the stationary phase.
the least attracted to the stationary phase.
the component with the heaviest particles.
the component with the lightest particles.
3. Which of the following analyses is NOT suited to analysis by gas chromatography?
A.
B.
C.
D.
Percentage of methane in natural gas
Percentage of vinyl chloride in air
Percentage of sugar in a can of cola
Percentage of ethanol in petrol
4. Two groups of students were analysing for the pigments present in the leaves of two different
plants using thin layer chromatography. They placed tiny spots of a solution extracted from
the leaves on the origin, and then sat the plates in the solvent.
Which of the following factors will NOT affect how high the spot corresponding to a
particular pigment will be located above the origin on the chromatogram?
A.
B.
C.
D.
The polarity of the molecules of the pigment
The particular solvent system used
The distance travelled by the solvent front
The concentration of the original spots of solution
5. A class was analysing the amino acid content of orange juice by thin layer chromatography.
Each group used the same solvent and same stationary phase.
In the chromatogram obtained by one group, the spot corresponding to a particular amino
acid was located 6.2 cm above the origin, while the solvent front was located at 8.0 cm.
What will be the height of the spot corresponding to the same amino acid in the
chromatogram obtained by another group, if their solvent front travelled 9.8 cm?
A.
B.
C.
D.
5.1 cm
6.2 cm
7.6 cm
8.0 cm
6. A mixture of methanol, CH3OH, and propanol, C3H7OH, was analysed by gas
chromatography. The concentration of methanol in this mixture was 80 %(v/v).
On the gas chromatogram, the peak for methanol will have:
A.
B.
C.
D.
the lower retention time and the higher area under the peak.
the lower retention time and the lower area under the peak.
the higher retention time and the higher area under the peak.
the higher retention time and the lower area under the peak.
7. Which factor from the following list will have the least influence on the retention time of a
particular constituent of a mixture that is analysed in the gas chromatograph?
A.
B.
C.
D.
The mass of the particles
The length of the column
The temperature of the column
The choice of carrier gas
8. A forensic chemist was analysing a white powder obtained in a criminal investigation. It was
suspected that the powder was a pure sample of a particular anabolic steroid.
For the analysis, the forensic chemist dissolved the sample in a pure solvent and injected it
into the gas chromatograph. The resulting gas chromatogram was then compared with one
obtained from a known pure sample of that steroid tested on the same instrument under the
same conditions.
What feature of the two gas chromatograms would confirm that the forensic sample is likely
to contain that particular steroid?
A.
B.
C.
D.
The total number of peaks
The retention times for the peaks
The area under each peak
The height of each peak
9. To analyse the caffeine content of a particular cola drink using high performance liquid
chromatography, the analyst first analysed pure caffeine and obtained the calibration graph
shown below.
Next she took a 100-mL sample of the drink and injected it into the column. The peak height
was 3.6. What is the total mass of caffeine per litre of the cola drink?
A.
B.
C.
D.
3 mg
12 mg
30 mg
120 mg
10. A sample of hydrocarbons, which contained a mixture of propane (C3H8), butane (C4H10),
and pentane (C5H12), was analysed in a gas chromatograph. The gas chromatogram shown
below was obtained.
What was the mole percentage of pentane in the mixture?
A.
B.
C.
D.
6%
30 %
33 %
67 %
11. Why does the liquid mobile phase used in HPLC need to be at high pressure?
A. It increases the adsorption of the constituents of the mixture onto the stationary
phase.
B. It increases the solubility of the constituents of the mixture in the mobile phase.
C. It enables the mixture under analysis to pass through the densely-packed column.
D. It increases the attraction between the molecules of the mixture and the solvent.
12. A burette was packed with finely powdered alumina (aluminium oxide). A solvent was run
through the column. Then a solution of an extract from a native fungus in the same solvent
was run through this column. The diagram below shows the result.
The same extract was then separated using thin layer chromatography. The stationary phase
used was a glass plate coated with finely divided alumina. Which of the components of the
mixture is likely to have the lowest Rf value in the thin layer chromatogram obtained?
A.
B.
C.
D.
Substance M
Substance N
Substance P
Substance Q
13. Which of the following separation techniques is limited to a qualitative analysis only?
A.
B.
C.
D.
Paper chromatography
Preparative thin layer chromatography
Gas chromatography
High performance liquid chromatography
14. In which of the following separation techniques does the separation usually take the longest?
A.
B.
C.
D.
Paper chromatography
Thin layer chromatography
Gas chromatography
High performance liquid chromatography
15. What was the very first type of analysis by fluid flow to be developed?
A.
B.
C.
D.
Paper chromatography
Thin layer chromatography
Gas chromatography
Column chromatography
16. Which of the following is NOT one of the reasons why the column used in gas
chromatography is located inside an oven?
A.
B.
C.
D.
The heat of the oven is used to convert a liquid mixture under analysis to a gas.
The heat of the oven speeds up the movement of the particles through the column.
The heat of the oven increases the rate of desorption from the stationary phase.
The heat of the oven ensures that the whole mixture elutes through the column.
17. Why is the column used in gas chromatography very narrow?
A.
B.
C.
D.
So the very long column takes up less space in the oven
To speed up the gas movement through the column
To decrease the amount of sample required for the analysis
To decrease the total surface area of the stationary phase
18. Why do constituents of a mixture that have a higher molecular mass take longer to elute
through a column in gas chromatography?
A.
B.
C.
D.
When injected in, they take longer to evaporate and enter the column
They move more slowly and stick more to the stationary phase
They stick less to the particles of the carrier gas
They stick more to one another and form clusters that are harder to move along
19. For a particular TLC plate, the pigment beta-carotene has an Rf value of 0.53 in a solvent
mixture of acetone and petrol. If, using this particular plate and solvent mixture, the height of
the spot corresponding to this pigment was 5.0 cm, how far did the solvent front move?
A.
B.
C.
D.
2.6 cm
5.5 cm
9.4 cm
10.6 cm
20. Which form of analysis can be used to purify relatively large quantities of a protein so that its
structure can then be determined?
A.
B.
C.
D.
Gravimetric analysis
Preparative thin layer chromatography
Gas chromatography
High performance liquid chromatography