CAIE IGCSE Chemistry Paper Chromatography and Rf Values
Practise setting up paper chromatography, interpreting spots and solvent fronts and calculating or comparing Rf values to identify mixture components.
- Syllabus
- 2026–2028
- Course
- Chemistry 0620
Exam points
- draw a pencil baseline above the solvent and place small concentrated sample spots on it
- interpret separated spots and compare unknown positions or Rf values with standards
- calculate Rf as distance travelled by the substance divided by distance travelled by solvent
Covered syllabus points
12.3 Chromatography question 1
Name the process used to:
identify the components of a mixture of soluble coloured substances
12.3 Chromatography question 2
Question (a)
(a)
Chromatography can be used to test the purity of substances.
The diagram shows the chromatogram of a coloured substance.
[ 3 ]
Question (i)
(i)
How does this chromatogram show that this substance is not pure?
[ 1 ]
Question (ii)
(ii)
Draw a circle round the correct value for the spot labelled X.
0.2
0.4
0.8
1.2
[ 1 ]
Question (iii)
(iii)
State how a colourless substance can be made visible on a chromatogram.
[ 1 ]
12.3 Chromatography question 3
Proteins are natural polymers.
Proteins are broken down into amino acids. The process is similar to how complex carbohydrates are broken down to give simple sugars.
Amino acids are colourless.
A sample containing a mixture of amino acids is separated. Each amino acid is detected and identified.
- Name the process used to separate the amino acids.
- Name the type of substance used to detect the amino acids.
- Give the symbol of the value used to determine the identity of each amino acid after separation and detection.
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