Question Video: Showing the Properties of Substances on Separate Compounds in the Paper Chromatography Chemistry

The given chromatogram shows that substance B has traveled further up the chromatography paper than substance A. What properties of a substance affect how far it will travel up the chromatography paper?

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Video Transcript

The given chromatogram shows that substance B has traveled further up the chromatography paper than substance A. What properties of a substance affect how far it will travel up the chromatography paper?

When we perform a chromatography experiment, the first thing that we do is place our samples on the chromatography paper. The particles in the sample get adsorbed to the chromatography paper, which means they get stuck to it. But this adsorption is not permanent. When we place the paper in the solvent, which could be water or something else, the solvent will begin to travel up the paper. As the solvent travels up the paper, some of the particles in the sample will dissolve in the solvent and travel up the paper with the solvent.

But what if the substance doesn’t dissolve very well? Well, that means that it won’t travel as far with the solvent as the solvent moves up the paper. So it seems that one factor that definitely affects how far a substance will travel up the paper is the solubility of the substance in the solvent. If it doesn’t dissolve in the solvent very well, it won’t be able to travel as far. And if it dissolves really easily, it will travel with the solvent as it moves up the paper very well.

Now, the other thing that’s going on besides how easily the substance dissolves in the solvent is how attracted the substance is to the paper. After all, adsorption is an attraction to the paper. The substance is stuck to it. So if the substance is really attracted to the paper, it won’t be able to move as far as the solvent travels up the chromatography paper. And if the substance is not very attracted to the paper, it will move more easily with the solvent. So the other property of a substance that affects how far it will move up the paper is how attracted it is to the paper. So knowing this, we can tell that substance B either dissolves more easily in the solvent or it’s less attracted to the paper than substance A.

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