Describe separation techniques for:(i) sublimation(ii) use of a separating funnel(iii) paper chromatography

Done by: Chew Yun Jin (3)3H/2011

Websites for extra information : http://www.youtube.com/watch?v=aFONmzLQJSY&

How do we separate immiscible liquids?To separate immiscible liquids, we use a separating funnel.For example, to separate oil and water, we use the following procedure:

1. Pour the mixture of oil and water into the separating funnel. (make sure the tap is closed)

2. Support the separating funnel using a retort stand. Then place a clean beaker below the separating funnel.

3. Allow the liquids to separate completely. This may take some time. The denser liquid (water) will be the bottom layer

4. Open the tap of the funnel to allow the bottom layer to drain into the beaker. Close the tap before the top layer of liquid runs out

5. Place another beaker below the funnel. Open the tap to allow a little of the top layer of liquid into the beaker. Dispose of the liquid collected. Now, the separating funnel contains only oil while the beaker from step 4 contains only water.

Paper Chromatography

The technique of using a solvent to separate a mixture into its components is called chromatography.

There is another way that paper chromatography is used to separate the dyes in the ink,. This method allows the solvent to ascend or travel up the chromatography paper.

Paper Chromatography

How does chromatography work?A spot of food colouring is applied to the chromatography paper.Once the chromatography paper is dipped in ethanol (the solvent). It soaks up ethanol.Ethanol that is soaked up by the paper dissolves the dyes. It continues to travel up the paper, carrying the dyes along.A dye that is not very soluble in ethanol will not be carried far along the paper.Coloured spots are left in different places on the paper at the end of the experiment.

Dyes are also used

to colour cloth.

What are R values?Look at Fig. 3.8. It shows the chromatograms of the same substance but in Fig. 3.8 (b), chromatography was allowed to proceed for a longer time.

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1) Chemistry Matters (Marshall Cavendish) textbook

2) www.tangrox.pbworks.com

3) www.chemrox.pbworks.com

Done by:

Chew Yun Jin (3)3H/2011