Interpreting Chromatograms
2 guided lessons · 18 checks · 1. Principles of Chemistry → Elements, Compounds & Mixtures
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Reading the Spots
A chromatogram is the finished paper after a run, and it reads like a list of ingredients. One spot means a pure substance; several spots mean a mixture, because each component travels to its own height. Run known compounds alongside as reference spots, and any unknown whose dots line up horizontally with a reference is named.
What you know already
You already know from Separation Techniques how paper chromatography separates the components of an ink. This note reads the result: what the spots say about purity and composition, and how Rf values put numbers on each component so unknowns can be named.
Key points of understanding
- A pure substance produces one spot on a chromatogram; an impure sample produces more than one.
- A mixture separates on the paper, showing each of its components as a separate spot.
- Identical substances produce identical chromatograms under the same conditions.
- A known compound run as a reference spot helps match and identify unknown spots.
- The brown ink's three dots line up horizontally with red, yellow and blue, so the ink contains all three.
- Exam chromatograms are black and white, so matching is done by horizontal alignment of dots.
Diagram showing the analysis of a mixture and pure substances using chromatography
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1.Reading the Spots
A chromatogram is the finished paper after a run, and it reads like a list of ingredients. One spot means a pure substance; several spots mean a mixture, because each component travels to its own height. Run known compounds alongside as reference spots, and any unknown whose dots line up horizontally with a reference is named.
Diagram showing the analysis of a mixture and pure substances using chromatography
Key points
- A pure substance produces one spot on a chromatogram; an impure sample produces more than one.
- A mixture separates on the paper, showing each of its components as a separate spot.
- Identical substances produce identical chromatograms under the same conditions.
Guided content from the SME authoring corpus — note rn_R3ptwxGTTvdBFvyP, pinned at 96c261a3a06e · promoted SyllabAI/syllabai-resources e967e75f1339
