Practical Tests

• Lithium = Red

• Sodium = Yellow

• Potassium = Lilac

• Iron = Gold

• Magnesium = Bright White

• Source of errors for flame tests:

• The test cannot detect low concentrations of most ions.

• The brightness of the flames varies from one sample to another. 

• Impurities or contaminants affect the test results. 

• The test cannot differentiate between all elements or compounds.

• Principle: Difference in solubility separates different pigments.

• Drop substance to centre of filter paper and allow it to dry

• Drop water on substance, one drop at a time

• Paper + rings = chromatogram. 

• Stationary phase: material on which the separation takes place

• Mobile phase: mixture you want to separate, dissolved in a solvent.

• Interpreting simple chromatograms:

• Number of rings/dots = number of substances

• If two dots travel the same distance up the paper they are the same substance.

RF Values-

Filtration-

• The mixture goes in a funnel with filter paper, into a flask.

• The residue is insoluble and filtrate goes through.

Crystallization-

• Some water in the solution is evaporated so solution becomes more

concentrated. 

• The solution is left to cool and crystallise. 

• Crystals are filtered to remove the solvent.