CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Qualitative Tests
Testing for the ammonium ion, sulfate and carbonate
- 3 things to know
- Unit AS 1
Overview
Test for the ammonium ion in a solid or solution, test for the sulfate ion and test for the carbonate ion.
What you need to know
Answer each one before you reveal it.
Write the ionic equation for the reaction that occurs when the ammonium ion is tested with sodium hydroxide.
Why can the ammonium ion not be identified by a flame test?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the test for the ammonium ion in a solid or solution.
Model answer
Sodium hydroxide solution is added and the mixture warmed, and the gas evolved turns damp red litmus paper blue.
- 2
Write the ionic equation for the reaction that occurs when the ammonium ion is tested with sodium hydroxide.
Model answer
The equation is NH₄⁺(aq) + OH⁻(aq) → NH₃(g) + H₂O(l).
- 3
Why must the mixture be warmed in the test for the ammonium ion?
Model answer
Warming drives the dissolved ammonia out of the solution so that enough gas escapes to be detected at the mouth of the tube.
- 4
Why can the ammonium ion not be identified by a flame test?
Model answer
The flame test detects the light emitted by metal ions, and the ammonium ion contains no metal.
- 5
Describe the test for the sulfate ion.
Model answer
Dilute hydrochloric acid is added and then barium chloride solution, and a white precipitate confirms a sulfate.
- 6
Write the ionic equation for the formation of the precipitate in the sulfate test.
Model answer
The equation is Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s).
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