Testing for chlorides (Cl^-), bromides (Br^-) and iodides (I^-)
3 marks · NormalExplain how you can distinguish between the precipitates formed when chloride, bromide or iodide ions react with silver nitrate. In your answer, refer to both the name and the colour of each precipitate.
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Silver chloride is white, silver bromide is cream, and silver iodide is yellow.
Also accept: The precipitate is silver chloride (white) for chloride ions, silver bromide (cream) for bromide ions, and silver iodide (yellow) for iodide ions.
Common mistakes: Mixing up which colour goes with which ion.; Giving only colour or only name, not both.
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Marking points
A1 · 1 mark · Correct colour and name for silver chloride (white)
A2 · 1 mark · Correct colour and name for silver bromide (cream)
A3 · 1 mark · Correct colour and name for silver iodide (yellow)
Worked solution
When silver nitrate is added to acidified solutions:
Chloride ions form a white precipitate of silver chloride (AgCl).
Bromide ions form a cream precipitate of silver bromide (AgBr).
Iodide ions form a yellow precipitate of silver iodide (AgI).