Give an equation for the reaction of solid sodium bromide with concentrated sulfuric acid to form bromine - AQA - A-Level Chemistry - Question 4 - 2021 - Paper 3
Question 4
Give an equation for the reaction of solid sodium bromide with concentrated sulfuric acid to form bromine.
Equation
Observation
A solution that is thought to cont... show full transcript
Worked Solution & Example Answer:Give an equation for the reaction of solid sodium bromide with concentrated sulfuric acid to form bromine - AQA - A-Level Chemistry - Question 4 - 2021 - Paper 3
Step 1
Equation
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Answer
The reaction between solid sodium bromide (NaBr) and concentrated sulfuric acid (H₂SO₄) is:
NaBr (s) + H2SO4(l)→NaHSO4(s)+HBr (g)
Further, HBr reacts to form bromine:
2HBr (g)→Br2(g)+H2(g)
Step 2
Observation
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Answer
The observation during this reaction is that orange or brown fumes are released due to the formation of bromine gas.
Step 3
1. Reason for the use of dilute nitric acid.
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Dilute nitric acid is used to remove any ions that may interfere with subsequent tests, such as halide ions.
Step 4
2. Reason for the use of aqueous silver nitrate.
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Answer
Aqueous silver nitrate is used to test for the presence of chloride or iodide ions, as it forms a precipitate with either of these ions.
Step 5
3. Reason for the use of excess dilute aqueous ammonia.
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Excess dilute aqueous ammonia is added to dissolve the silver chloride precipitate and further confirm the presence of chloride ions.
Step 6
Explain the observations.
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The pale yellow precipitate indicates the formation of silver bromide when AgNO₃ is added, while the darker yellow precipitate remaining indicates that some silver bromide does not dissolve in ammonia.
Step 7
Ionic equations for any reactions.
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Answer
The ionic equation for the reaction between silver nitrate and chloride ions is:
