Precipitation: Preparation of Insoluble Salts
15 Questions · 36 Total Marks · Recipe Selection, Paper 6 Methods & Drying
📋 How to use this paper
Read each question carefully, write your answer, then press Reveal Answer to check. Use the self-mark buttons to track your score. Every answer includes an Examiner Trap — the mistake students most commonly make.
Section A — The Recipe: Choosing Your Reagents
Name the correct reagent pairs to form each precipitate.
Name two solutions that could be mixed together to prepare a precipitate of barium sulfate, BaSO₄.
💡 Hint: Think: what ion does barium sulfate need? Which soluble salts provide Ba²⁺ and SO₄²⁻?
Name two solutions that could be mixed together to prepare a precipitate of silver chloride, AgCl.
💡 Hint: Which soluble salt provides Ag⁺? Which soluble salt provides Cl⁻?
Name two solutions that could be mixed together to prepare a precipitate of lead(II) sulfate, PbSO₄.
💡 Hint: Think: which lead salt is soluble? Which soluble sulfate can you use?
Name two solutions that could be mixed to prepare a precipitate of copper(II) hydroxide, Cu(OH)₂.
💡 Hint: Which ion does copper(II) hydroxide need? Which alkali provides OH⁻ without forming its own precipitate?
Name two solutions that could be mixed to prepare a precipitate of iron(III) hydroxide, Fe(OH)₃.
💡 Hint: Which iron salt is soluble? Which alkali provides OH⁻?
Section B — The Method: Separation & Purification
Describe the laboratory steps to separate and purify the product.
Describe how you would separate the precipitate from the reaction mixture after mixing the two solutions.
💡 Hint: This is a Paper 6 method question. Think: what apparatus do you need? What is the technique called?
After filtration, why should the precipitate be washed with distilled water?
💡 Hint: What unwanted substances remain on the precipitate after filtration?
A student pours a large excess of distilled water over the precipitate during washing. Explain why this could reduce the purity of the final product.
💡 Hint: What property of the precipitate does excess water exploit?
Describe the full Paper 6 method to prepare a pure, dry sample of barium sulfate starting from barium chloride solution and sodium sulfate solution.
💡 Hint: Think of this as a step-by-step recipe. Cover: mixing, filtering, washing, and drying.
Explain why the filtration method is used to separate the precipitate, rather than evaporation.
💡 Hint: What would happen if you tried to evaporate the mixture to get the precipitate?
Section C — Drying the Precipitate
Explain how to dry the precipitate safely and completely.
State two acceptable methods for drying the washed precipitate.
💡 Hint: Think about what you can do at school without expensive equipment.
Explain why a high-temperature furnace should NOT be used to dry the precipitate of barium sulfate.
💡 Hint: What could go wrong to the compound at very high temperatures?
Which of the following is the best method to check if the precipitate is completely dry?
Draw and label the apparatus used during the filtration step of this preparation. Your diagram must show: the funnel, filter paper, stand, and collection vessel.
💡 Hint: This is a Paper 6 diagram question. Check: is the filter paper folded correctly? Is the funnel stem touching the beaker wall?
Model Diagram (revealed with answer)
A student prepares silver chloride by mixing silver nitrate solution and sodium chloride solution. Describe in full the steps they should follow to obtain a pure, dry sample of silver chloride. Include any safety precautions.
💡 Hint: This is a 5-mark extended answer. Cover: mixing, observation, filtering, washing, drying, safety.
📊 Your Score
Self-marked. Reveal answers and mark yourself using the Yes/No buttons above. Cambridge grade boundary: A* ≥ 90%, A ≥ 80%, B ≥ 70%.
🧪 Solubility Rules — Quick Reference
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