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This question is about ion testing - AQA - A-Level Chemistry - Question 8 - 2017 - Paper 1
Question 8
This question is about ion testing. 08.1 Describe how a student could distinguish between aqueous solutions of potassium nitrate, KNO₃, and potassium sulfate, K₂SO₄... show full transcript
Worked Solution & Example Answer:This question is about ion testing - AQA - A-Level Chemistry - Question 8 - 2017 - Paper 1
Step 1
Describe how a student could distinguish between aqueous solutions of potassium nitrate, KNO₃, and potassium sulfate, K₂SO₄, using one simple test-tube reaction.
Answer
To distinguish between potassium nitrate (KNO₃) and potassium sulfate (K₂SO₄), the student can use a sodium hydroxide solution as a reagent.
- Reagent: Sodium hydroxide (NaOH).
- When NaOH is added to KNO₃, there will be no visible precipitation or change; the solution remains colorless.
- When NaOH is added to K₂SO₄, a white precipitate of barium sulfate (BaSO₄) will form, indicating the presence of sulfate ions.
Step 2
Describe how a student could distinguish between aqueous solutions of magnesium chloride, MgCl₂, and aluminium chloride, AlCl₃, using one simple test-tube reaction.
Answer
To distinguish between magnesium chloride (MgCl₂) and aluminium chloride (AlCl₃), the student can again use sodium hydroxide as the reagent.
- Reagent: Sodium hydroxide (NaOH).
- When NaOH is added to MgCl₂, a white precipitate of magnesium hydroxide (Mg(OH)₂) will form.
- When NaOH is added to AlCl₃, initially there will be a white precipitate of aluminium hydroxide (Al(OH)₃) which may dissolve in excess NaOH, demonstrating a difference in behavior.