Specification Point 9.2C:
Describe flame tests to identify the following ions in solids:
a) lithium ion, Li+ (red)
b) sodium ion, Na+ (yellow)
c) potassium ion, K+ (lilac)
d) calcium ion, Ca2+ (orange-red)
e) copper ion, Cu+ (blue-green)
- Metal ions produce a colour if heated strongly in a flame.
- Ions from different metals produce different colours.
- The flame test is thus used to identify metal ions by the colour of the flame they produce.
- Dip the loop of an unreactive metal wire such as nichrome or platinum in dilute acid and rinse with distilled water.
- This cleans the wire loop and avoids contamination. This is an important step as the test will only work if there are just one type of ion present.
- Two or more ions means the colours will mix, making identification difficult and erroneous.
- Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame.
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.
The colours formed in the flame test for metal ions
Edexcel GCSE Chemistry Notes
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