Testing for Halide ions

Halide ion tests and results

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  • Created by: k spear
  • Created on: 15-01-14 16:09


This is a simple test tube test to detect halide ions.

  • the unknown halide substance is dissovled in water
  • an aqueous solution of silver nitrate (AgNO3 (aq) is added
  • the silver (Ag+) ions from the silver nitrate react with any halide ions that are present, froming a silver halide precipitate, AgX (s) 
  • These precipitates are coloured, each colour being specific to one halide.
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Test (part 2)

Sometimes it is hard to tell the difference between the coloured silver halide precipitates. If this is the case there is another part to the test

  • if you are unsure, then add aqueous ammonia, NH3 (aq)
  • different halides precipitates have different soluabilities in aqeous ammonia - this can then confirm which halide ion is present.
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The results

Halide test results are:

  • Chloride= white precipitate, soluble in dilute aqueous ammonia
  • Bromide= cream precipitate, soluble in concentrated aqueous ammonia
  • Iodide= yellow precipitate, insoluble in concentrated aqueous ammonia
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Ionic equations

You also need to know the ionic equations for each reaction

  •  Chloride = Ag+ (aq) + Cl- (aq) --> AgCl (s)
  • Bromide = Ag+ (aq) + Br- (aq) --> AgBr (s)
  • Iodide = Ag+ (aq) + I- (aq) --> AgI (s)
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This type of reaction is called a precipitate reaction.

A Precipitate reaction is the formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together.

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