How to Carry Out a Flame Test (Edexcel IGCSE Chemistry (Modular))
Revision Note
Flame tests
The flame test is used to identify the positive metal ion (cations) by the colour of the flame they produce
Ions from different metals produce different colours
To carry out a flame test:
Dip the loop of an unreactive metal wire such as nichrome or platinum in dilute acid
Hold it in the blue flame of a Bunsen burner until there is no colour change
Dip the loop into the solid sample / solution and place it in the edge of the blue Bunsen flame
It is important to place the wire into acid first to prevent contamination
Not doing this might result in two or more ions being present on the wire meaning the colours will mix
One colour could mask another colour and you will not be able to identify the ion
Diagram showing the technique for carrying out a flame test
The colour of the flame is observed and used to identify the metal ion present
Cation | Flame Colour |
---|---|
Li+ | Red |
Na+ | Yellow |
K+ | Lilac |
Ca2+ | Orange-red |
Cu2+ | Blue-green |
Diagram showing the colours formed in the flame test for metal ions
Examiner Tip
The sample needs to be heated strongly, so the Bunsen burner flame should be on a blue flame.
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