Testing for chlorides (Cl^-), bromides (Br^-) and iodides (I^-)
5 marks · HardWhen silver nitrate solution is added to separate solutions of sodium chloride, sodium bromide and sodium iodide (each has first been acidified with dilute nitric acid), different precipitates form.
For each solution, name the precipitate formed and state its colour.
Sodium chloride solution:
Sodium bromide solution:
Sodium iodide solution:
Give the chemical formula for the precipitate formed in each case.
From sodium chloride:
From sodium iodide:
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a(i)) Silver chloride (white)
(a(ii)) Silver bromide (cream)
(a(iii)) Silver iodide (yellow)
(b(i)) AgCl
(b(ii)) AgI
Common mistakes: Mixing up colours (e.g. writing white for AgBr or AgI); Giving incorrect formulae (e.g. NaCl for the precipitate rather than AgCl)
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Marking points
B1 (a(i)) · 1 mark · States: Silver chloride, white
B2 (a(ii)) · 1 mark · States: Silver bromide, cream
B3 (a(iii)) · 1 mark · States: Silver iodide, yellow
B4 (b(i)) · 1 mark · States: AgCl
B5 (b(ii)) · 1 mark · States: AgI
Worked solution
a) On adding silver nitrate to acidified sodium chloride: the precipitate is silver chloride, which is white.
On adding silver nitrate to acidified sodium bromide: the precipitate is silver bromide, which is cream.
On adding silver nitrate to acidified sodium iodide: the precipitate is silver iodide, which is yellow.
b) The formulas are: AgCl (from sodium chloride), AgI (from sodium iodide).