Testing for chlorides (Cl^-), bromides (Br^-) and iodides (I^-)
2 marks · HardDescribe the steps you would take to test a solution to determine whether it contains any halide ions (chloride, bromide, or iodide) using silver nitrate.
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Also accept: Add a few drops of dilute nitric acid to the solution, then add a few drops of silver nitrate solution. Observe if a precipitate forms. If a precipitate forms, a halide ion is present.; First, add dilute nitric acid to the solution to remove interfering ions. Next, add silver nitrate solution. If a precipitate appears, this shows the presence of a halide ion.
Common mistakes: Omitting addition of nitric acid; Not stating both steps; Saying to use hydrochloric acid (incorrect)
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Marking points
M1 · 1 mark · Mentions adding dilute nitric acid to the solution first.
M2 · 1 mark · Mentions adding silver nitrate solution after the acid.
Worked solution
Add a small amount of dilute nitric acid to the solution being tested. Then add a few drops of silver nitrate solution. If a precipitate forms (white, cream, or yellow), this indicates the presence of chloride, bromide, or iodide ions, respectively.