This definitions covers Key Definitions within Tests for Ions for GCSE Chemistry. Revise Tests for Ions in Chemical Analysis for GCSE Chemistry with 20 exam-style questions and 14 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
📖 Key Definitions
Precipitate: An insoluble solid formed when two solutions are mixed together. It appears as a cloudiness or solid particles settling out of solution.
Precipitation reaction: A reaction between two aqueous solutions that produces an insoluble product (precipitate). General form: A⁺(aq) + B⁻(aq) → AB(s)
Qualitative analysis: Chemical analysis that identifies WHAT substances are present (as opposed to quantitative analysis, which measures HOW MUCH is present).
Spectator ions: Ions that are present in solution during a reaction but do not take part in the reaction. They can be removed from the full ionic equation to give the net ionic equation.
False positive: A test result that incorrectly indicates the presence of a substance. Prevented in sulfate and halide tests by adding acid to remove interfering ions.
Practice questions for Tests for Ions
Which reagents are used to test for carbonate ions in a solution?
Describe how sodium hydroxide solution can be used to distinguish between iron(II) ions and iron(III) ions in solution, including the expected observations.