Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed
Preparing an Insoluble Salt — exam questions
12 original Incandio exam-style questions on Preparing an Insoluble Salt, 26 marks, about 26 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Preparing an Insoluble Salt — the lesson that teaches it. Read the lesson first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
8 command words run through this set, and on Pearson Edexcel International GCSE Chemistry each one means something precise. Answering the wrong command is the commonest way a candidate who understands the lesson still loses the mark.
- Which (1 mark)
- one option chosen from the set given
- State (1 mark)
- one precise fact, no justification
- Give (1–2 marks)
- a short factual answer — the most common chemistry command
- Describe (2–5 marks)
- developed, linked statements of what happens or what is observed Misread as: giving one bare observation where the tariff asked for a developed account
- Explain (2–4 marks)
- the reason, in terms of particles, bonding, energy or equilibrium Misread as: describing the observation without giving the chemistry that causes it
- Compare (2–4 marks)
- explicit comparison with a comparative word — a bare pair of statements is not a comparison
- Suggest (1–3 marks)
- a plausible answer applying taught chemistry to an unfamiliar substance
- Name (1 mark)
- the correct chemical name
Assessed on Paper 1 (4CH1/1C) and Paper 2 (4CH1/2C), against AO1, AO2, AO3.
Where these sit in the specification
Pearson Edexcel International GCSE Chemistry (4CH1) — statements 2.41 · 2.43. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 12 questions
Answer them on paper, then open the lesson's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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A student prepared a pure dry sample of lead(II) sulfate. She mixed a solution of lead(II) nitrate with a solution of sodium sulfate, stirred, and a white solid appeared at once. She then filtered the mixture, washed what was left on the filter paper, and left it in a warm oven.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(a)
(1)Name
Name the substance dissolved in the filtrate the student threw away.
A student prepared a pure dry sample of lead(II) sulfate. She mixed a solution of lead(II) nitrate with a solution of sodium sulfate, stirred, and a white solid appeared at once. She then filtered the mixture, washed what was left on the filter paper, and left it in a warm oven.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(b)
(2)Explain
Explain how the solubility rules predict which of the two possible products is the white solid.
A student prepared a pure dry sample of lead(II) sulfate. She mixed a solution of lead(II) nitrate with a solution of sodium sulfate, stirred, and a white solid appeared at once. She then filtered the mixture, washed what was left on the filter paper, and left it in a warm oven.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(c)
(3)Explain
Explain why no evaporation or crystallisation step was needed in the student's method.
A student prepared a pure dry sample of lead(II) sulfate. She mixed a solution of lead(II) nitrate with a solution of sodium sulfate, stirred, and a white solid appeared at once. She then filtered the mixture, washed what was left on the filter paper, and left it in a warm oven.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(d)
(3)Suggest
The student's dried sample weighed more than the mass of lead(II) sulfate that could have formed. Suggest two reasons.
A student prepared a pure dry sample of lead(II) sulfate. She mixed a solution of lead(II) nitrate with a solution of sodium sulfate, stirred, and a white solid appeared at once. She then filtered the mixture, washed what was left on the filter paper, and left it in a warm oven.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(Total for Question 1 = 9 marks)
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(1)Which
Which term describes the solid that forms when two solutions are mixed?
Term A a filtrate B a precipitate C a residue of reactant D a solvent (Total for Question 2 = 1 mark)
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(1)State
State why both starting solutions must be soluble in water.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(Total for Question 3 = 1 mark)
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(1)Give
Give the liquid that should be used to wash the precipitate.
(Total for Question 4 = 1 mark)
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(2)Describe
Describe the steps needed to obtain a dry sample of an insoluble salt once the two solutions have been mixed.
(Total for Question 5 = 2 marks)
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(3)Explain
Explain why the precipitate must be washed before it is dried.
(Total for Question 6 = 3 marks)
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(2)Compare
Compare the way the product is collected in this preparation with the way it is collected when a soluble salt is made.
(Total for Question 7 = 2 marks)
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(3)Suggest
Suggest two solutions that could be mixed to prepare barium sulfate, and give a reason for each choice.
Solubility rules — All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. Chlorides are soluble except silver and lead. Sulfates are soluble except barium, calcium and lead.
(Total for Question 8 = 3 marks)
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(4)Explain
Explain why an insoluble salt is made by precipitation rather than by reacting an acid with a metal oxide.
(Total for Question 9 = 4 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 12 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain Preparing an Insoluble Salt to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Jöns Jacob Berzelius over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Preparing an Insoluble Salt — Mix two solutions, and the salt you want falls out of them as a solid.
- All of Incandio Chemistry · Incandio Exam Practice