Summary
Qualitative analysis involves identifying ions through specific tests, such as flame tests for metal ions and precipitation reactions for cations and anions.
- Flame Test — a method to identify metal ions based on the color they produce in a flame. Example: Lithium ions produce a red flame.
- Sodium Hydroxide Test — used to identify metal cations by the color of the precipitate formed. Example: Iron (III) ions form a rust-brown precipitate.
- Test for Ammonium Ions — involves heating with sodium hydroxide to release ammonia gas. Example: Ammonia gas turns moist red litmus paper blue.
- Halide Test — uses silver nitrate to identify halide ions by the color of the precipitate. Example: Chloride ions form a white precipitate.
- Carbonate Test — involves reaction with dilute acid to produce carbon dioxide. Example: Carbon dioxide turns limewater milky.
- Sulfate Test — involves adding barium chloride to form a white precipitate. Example: Sulfate ions form a white precipitate with barium chloride.
Exam Tips
Key Definitions to Remember
- Flame test colors for metal ions
- Precipitate colors for cation tests with NaOH
- Reactions of anions with specific reagents
Common Confusions
- Mixing up flame test colors for similar ions
- Misidentifying precipitate colors
Typical Exam Questions
- What color is the precipitate formed when sodium hydroxide is added to iron (III) ions? Answer: Brown
- What is the flame test color of potassium? Answer: Lilac
- What would the polymer formed from ethene monomers be called? Answer: Poly(ethene)
What Examiners Usually Test
- Ability to identify ions based on test results
- Understanding of the procedures for qualitative analysis