EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:2.7.2 Flame Tests

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:2.7.2 Flame Tests

Flame Tests

 

  • 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 concentrated acid, and then hold it in the blue flame of a Bunsen burner until there is no colour change
  • This cleans the wire loop and avoids contamination
    • This is an important step as the test will only work if there is just one type of ion present
    • Two or more ions means the colours will mix, making identification erroneous

     

  • Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame
  • Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour

 

 

Identifying-Metal-Cations

 

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

 

8.3.1-FlameTest-Results

 

 

Colours-of-metal-cations

 

Diagram showing the colours formed in the flame test for metal ions

 

 

Exam Tip

The sample needs to be heated strongly, so the Bunsen burner flame should be on a blue flame.

转载自savemyexams

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