In the qualitative analysis procedure, the chemical properties of an unknown substance are determined by systematically reacting the unknown with a number of different reagents to test for reactions characteristic of certain ions, which may cause color change, solid forming and other visible changes.
By predetermining what the particular reaction will produce if a specific ion is present, the ions that actually are in the solution can be identified. For example, if a reaction is known to produce a precipitate if ion A is present and a precipitate is formed when the reaction is run, then ion A may be present in solution (there may be, and usually are, other ions that will also precipitate with a particular reagent). If no precipitate is formed when the reaction is run, then ion A is clearly not present in the unknown solution and a different reaction will have to be run to determine what ions are present.
There are two general situations in which qualitative analysis is used - in the identification of a simple salt, or the identification of multiple cations in a solution.
The basic testing procedure for identifying a salt is as follows.
1. Appearance of compound
- color and shape of the crystals
2. Heating effect
3. Flame test
4. Solubility in water
5. Reaction with sodium hydroxide
6. Reaction with ammonia
7. Reaction with hydrochloric acid
8. Reaction with sulfuric acid
9. Reaction with silver nitrate
10. Reaction with barium nitrate
11. Specific/Confirmatory Tests - Cation Identification Tests
- Anion Identification Tests
Sample Z had the following characteristics:
Conclusion: Sample Z is ____________ (answer in forum : Form 4)
Download 1 page short note for qualitative analysis of salts. (link updated 9/9/2012)