To test a solution for chloride ions, it is first acidified with dilute nitric acid. Which reagent is then added?
Question 1 Report
To test a solution for chloride ions, it is first acidified with dilute nitric acid. Which reagent is then added?
Answer Details
Halide ions are tested with aqueous silver nitrate after acidifying with dilute nitric acid. Silver ions react with chloride ions to give insoluble silver chloride, seen as a white precipitate: \( \mathrm{Ag^+ + Cl^- \rightarrow AgCl} \).
The nitric acid is added first to remove carbonate or sulfite ions, which would otherwise form their own silver precipitates and give a false positive. Hydrochloric acid must never be used, because it would add the very chloride ions being tested for.
Barium nitrate is the reagent for sulfate ions, limewater tests for carbon dioxide gas, and aqueous sodium hydroxide identifies metal cations rather than halides.
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