Key term
Edexcel A-Level Chemistry 9CH0
Atomic Structure and the Periodic Table
Bonding and Structure
Inorganic Chemistry and the Periodic Table
Topic overviewFlame tests and how they workThermal decomposition of nitrates and carbonatesCarrying out flame tests and testing the gasesGroup 2 elements and their compoundsTrends in Group 7 and predicting fluorine and astatineHalogen displacement reactionsDisproportionation and the reactions of chlorineHalides with concentrated sulfuric acid, and the hydrogen halidesTesting for halide ions with silver nitrateTesting for carbonate and hydrogencarbonate ionsTesting for sulfate and ammonium ions
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Organic Chemistry I
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Organic Chemistry III
Topic overviewThe structure of benzene and the evidence for itElectrophilic substitution of benzeneNitration, halogenation, Friedel-Crafts and phenolAmines: structure and basicityReactions of amines and preparing themAmides and condensation polymersAmino acids, zwitterions and proteinsEmpirical and molecular formulae from analytical dataGrignard reagents and multi-step synthesisPurification techniques and the aspirin preparation
Inorganic Chemistry and the Periodic Table
Testing for sulfate and ammonium ions
- 3 things to know
- Papers 1 and 3
Overview
The acidified barium chloride test for sulfate ions with its white barium sulfate precipitate and ionic equation, why hydrochloric acid is added first to stop carbonate and sulfite ions giving false positives, and the test for ammonium ions by warming with sodium hydroxide, its ionic equation, and identifying the ammonia with damp red litmus or by smell.
What you need to know
Answer each one before you reveal it.
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Key term
State the ionic equation for the reaction between ammonium ions and hydroxide ions.
Key term
In the test for sulfate ions, what acid is used to acidify the sample before adding barium chloride?
Questions from this subtopic
Each one with the model answer underneath.
- 1
After acidifying a sample, what reagent is added to test for sulfate ions?
Model answer
Barium chloride solution
- 2
What is the positive result when testing for sulfate ions with acidified barium chloride?
Model answer
A white precipitate of barium sulfate forms
- 3
Write the ionic equation for the precipitation reaction in the sulfate ion test.
Model answer
Ba²⁺ + SO₄²⁻ → BaSO₄
- 4
What is the formula of the precipitate formed in the test for sulfate ions?
Model answer
BaSO₄
- 5
In the test for sulfate ions, what acid is used to acidify the sample before adding barium chloride?
Model answer
Dilute hydrochloric acid
- 6
Why is the sample acidified with hydrochloric acid before adding barium chloride in the sulfate test?
Model answer
To prevent false positives from carbonate or sulfite ions, which would otherwise form barium precipitates
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