HCl Test Using Silver Chloride
A chloride gives itself away in one step: silver nitrate solution, added to anything carrying a chloride ion, throws down silver chloride as a curdy white precipitate that will not dissolve in cold water or in dilute nitric acid. This activity runs the test on dilute hydrochloric acid — acidifying with dilute nitric acid first, the standard step that keeps other precipitates out of the way — and then adds excess ammonia solution, which dissolves silver chloride and nothing else that looks like it. That solubility, not the precipitate alone, is what a chemist actually trusts.
4 steps · Hydrogen Chloride · Study of Compounds
What you will use
Apparatus
- Flask
Chemicals
- Dilute Hydrochloric Acid
- Dilute Nitric Acid
- Silver Nitrate Solution
- Ammonia Solution
The steps
-
Pour dilute hydrochloric acid into the flask.
Colourless. Nothing about it yet suggests what it contains.
-
Acidify with dilute nitric acid.
Still colourless. Nitric acid does not react with hydrochloric acid; it only clears the way for the real test.
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Add silver nitrate solution.
A curdy white precipitate forms at once: silver chloride.
-
Add ammonia solution, in excess.
The white precipitate dissolves and the flask clears.
What it shows
The precipitate is silver chloride, formed the instant silver nitrate meets a chloride ion. It resists cold water and dilute nitric acid but dissolves in excess ammonia, forming a soluble diammine silver complex — that pattern of insoluble-then-soluble is the actual confirmation, and the same test on dilute nitric acid would give no precipitate at all, which is how the two dilute acids are told apart.