An aqueous sample containing the following anions is analysed - HSC - SSCE Chemistry - Question 10 - 2011 - Paper 1
Question 10
An aqueous sample containing the following anions is analysed.
Cl⁻
CO₃²⁻
SO₄²⁻
In which order should the reagents be added to determine the amount of chlorid... show full transcript
Worked Solution & Example Answer:An aqueous sample containing the following anions is analysed - HSC - SSCE Chemistry - Question 10 - 2011 - Paper 1
Step 1
Reagent 1: HNO₃
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Answer
The first reagent to be added is HNO₃ (Nitric acid). This acid will help to react with any carbonates present in the sample, thus preventing the precipitation of any silver chloride before the presence of other anions is determined.
Step 2
Reagent 2: Ba(NO₃)₂
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Next, Ba(NO₃)₂ (Barium nitrate) should be added. This will precipitate sulfate ions as BaSO₄, allowing for the detection of chloride without interference from sulfate.
Step 3
Reagent 3: AgNO₃
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Finally, AgNO₃ (Silver nitrate) is added to react with any remaining chloride ions in the solution, forming a white precipitate of AgCl. This confirms the presence of chloride in the sample.
