Particles and Mixtures - 1.8 Paper Chromatography

What is chromatography?

Chromatography is a chemical analysis technique, used to seperate substances is a mixture

What is paper chromatography used for?

To separate a mixture of substances based on their solubility in a solvent

What is the name given for the pencil line in paper chromatography?

The baseline

When doing paper chromatography, why should we use pencil for the baseline rather than pen?

Pen ink would dissolve in the solvent and move up the paper.

What are the 2 phases of chromatography?

1. Mobile phase - in which molecules can move, usually a liquid or gas

2. Stationary phase - in which molecules can't move, usually a solid or really thick liquid

When doing paper chromatography, what determines the amount of time molecules spend in the mobile and stationary phases?

1. How soluble they are in the solvent (mobile phase).

2. How attracted they are to the paper (stationary phase).

When doing paper chromatography, what happens to chemicals that have greater solubility in the mobile phase?

A substance which is more soluble in the mobile phase will spend more time in the mobile phase. This means it will move faster, and therefore travel a further distance up the paper than a less soluble chemical.

What is the formula to calculate an Rf value,from a chromatogram?

Rf = distance travelled by substance / distance travelled by solvent