More Lessons for IGCSE Chemistry
A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).
The following table shows the tests for water, acids, bases, alkanes and alkenes.
Testing for alkanes / alkenes by the addition of Bromine
Alkenes changes the bromine water from brown to colourless.
Alkanes do not react with the bromine water.
Testing for the presence of water
Water will turn anhydrous copper(II) sulfate from white to blue and anhydrous cobalt(II) chloride from blue to pink.
To decide whether it is pure water, test to show that the boiling point is exactly 100°C.
Test for ethanol and ethanoic acid
Ethanol and ethoic acid reacts with each other, with the addition of a few drops of concentrated sulfuric acid, to produce a sweet-smelling ester.
Chromatography can be used for separating coloured substances. It can also be used to separate amino acids (monomers) from proteins and sugars from carbohydrates. Since these compounds are colourless, the spots must be detected using locating agents. If a sample gives only a single spot, then it is an indication that it might be pure. It would be better to check, using different solvents for confirmation.
The identity of the compound can be confirmed by measuring the Rf
value in the solvent being used.
Paper and Thin Layer Chromatography
Chromatography for Amino Acids
Chromatography for Sugars
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