Question

organic chemistry - PLEASE HELP

Answer 1

Chromatography can be used to purify samples. One way of doing this involves the use of very large plates (20cmx20cm) upon which the sample is placed as a line or stripe near the bottom. Explain how these plates can be used to isolate small samples that are quite pure (outline the steps required)
HINTS: The silica can be scraped off the plastic or glass backing. The silica is not soluble in organic solvents.

Answer 2

this is analytical chemistry, not organic... Regardless, you're probably talking about "thin-layer chromatography", in which you have a silica plate (hydrophilic) as your stationary phase and a non-polar solvent (or mixture of solvents) as your mobile phase. The plate is immersed into a vessel containing the eluting solvent (mobile phase), which travels up the plate through capillary action.

A given analyte will interact preferentially with one of the phases and be, either, retarded by interaction with the stationary phase (the silica plate) or interact poorly with the stationary phase and be carried by the eluting solvent.

You can make the assertion that the further a given analyte travels the more non-polar it is.

So, if you have impure sample, you can separate it into it's different components, given that the substances present have different polarities.