SS1 Chemistry Lesson Note on Separating Immiscible Liquids

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PERIOD 3. SEPARATING IMMISCIBLE LIQUIDS (USING SEPARATING FUNNEL METHOD)

This a method used to separate a mixture of immiscible liquids e.g. a mixture of petrol and water. When the two liquids are added together they do not mix, instead they separate into two distinct layers, a lower denser layer and an upper less dense layer in the funnel as below.

EVALUATION:

Draw a labeled diagram to show how you would separate a mixture of kerosene and water.

PERIOD 4: CHROMATOGRAPHY

Separating complex mixtures by chromatography: This is a method of separation of the components of mixtures of solutes from a solution (mixture) using a solvent (liquid) moving over a porous, adsorbent medium e.g. filter paper or gel. This method can be mixtures f soluble substances. There are different types of chromatographic methods. Paper chromatography (ascending paper chromatography), column chromatography, thin layer chromatography and gas chromatography.

ASCENDING PAPER CHROMATOGRAPHY

As shown in the above diagram, the apparatus include: a glass jar with lid, filter paper, clips, solvent (water or ethanol). The solution containing the mixture of solutes to be separated is spotted unto the strips of paper near one end.

The paper is then suspended in a closed air- tight jar with the spotted end (but not the spot) dipping into the solvent. As the solvent ascends the paper the different solutes in the mixture gets dissolved and also more along the paper strip at different speeds and hence become separated. The paper strip is removed from the jar when the solvent has moved about three-quarters way up the strip. It is dried and if necessary sprayed with appropriate chemical reagents to locate the positions of the various along the strip. Each solute can then be identified by the distance it has traveled. This is done by comparing its distance with those of known standard substances.

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