BRAINCAKEDistinguishing Silver Halides with Ammonia
Because the colours of the silver halide precipitates can be hard to tell apart, ammonia solution is added to the precipitate to confirm which halide is present. The silver halides dissolve in ammonia to different extents:
AgCl (white): dissolves in dilute ammonia, giving a colourless solution.
AgBr (cream): does not dissolve in dilute ammonia, but dissolves in concentrated ammonia.
AgI (yellow): insoluble even in concentrated ammonia.
A precipitate dissolves because ammonia molecules bond to the silver ions, forming a soluble complex ion, the diamminesilver(I) ion:
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Key terms in this lesson
- complex ion
- An ion formed when a metal ion bonds to one or more ligands by dative covalent bonds.
More in Group 7
- Reaction with Water
- Reaction with Alkali
- Example Question - 1
- Example Question - 2
- Example Question - 3
- Silver Nitrate Test for Halide Ions
- Colours of Silver Halide Precipitates
- Why Nitric Acid is Added First
All 20 lessons in Group 7 · All AQA AS-level Chemistry topics