Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed
Solubility and Solubility Curves — exam questions
11 original Incandio exam-style questions on Solubility and Solubility Curves, 22 marks, about 22 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 Solubility and Solubility Curves — 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
6 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
- 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
- Calculate (1–4 marks)
- a numerical answer with working, to the stated precision
- 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
- Suggest (1–3 marks)
- a plausible answer applying taught chemistry to an unfamiliar substance
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 1.5 · 1.6 · 1.7. 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 11 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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Table 1 — the solubility of two salts, in g per 100 g of water. Temperature / °C Salt A Salt B 10 21 35.8 30 46 36.3 50 85 37.0 70 138 37.8 (a)
(1)Give
Give the salt in Table 1 whose solubility changes least with temperature.
Table 1 — the solubility of two salts, in g per 100 g of water. Temperature / °C Salt A Salt B 10 21 35.8 30 46 36.3 50 85 37.0 70 138 37.8 (b)
(2)Calculate
Calculate the mass of salt A that would dissolve in 250 g of water at 50 °C.
Table 1 — the solubility of two salts, in g per 100 g of water. Temperature / °C Salt A Salt B 10 21 35.8 30 46 36.3 50 85 37.0 70 138 37.8 ............................ g
(c)
(3)Explain
Explain how a mixture of salt A and salt B could be separated using the data in Table 1.
Table 1 — the solubility of two salts, in g per 100 g of water. Temperature / °C Salt A Salt B 10 21 35.8 30 46 36.3 50 85 37.0 70 138 37.8 (d)
(2)Suggest
Suggest why the crystals of salt A obtained this way would not be completely pure.
Table 1 — the solubility of two salts, in g per 100 g of water. Temperature / °C Salt A Salt B 10 21 35.8 30 46 36.3 50 85 37.0 70 138 37.8 (Total for Question 1 = 8 marks)
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(1)Which
Which unit is solubility measured in?
Unit A g per 100 g of water B g per dm³ C mol per dm³ D g per second (Total for Question 2 = 1 mark)
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(1)Give
Give the solubility of potassium nitrate at 40 °C, using Figure 1.
Figure 1 — the solubility of potassium nitrate in water at different temperatures. Plotted as a line; the graph is drawn in Incandio and the readings are below. Temperature / °C Solubility / g per 100 g of water 0 13 10 21 20 32 30 46 40 64 50 85 60 110 solubility of potassium nitrate = ............................ g per 100 g of water
(Total for Question 3 = 1 mark)
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(2)Describe
Describe the relationship shown in Figure 1.
Figure 1 — the solubility of potassium nitrate in water at different temperatures. Plotted as a line; the graph is drawn in Incandio and the readings are below. Temperature / °C Solubility / g per 100 g of water 0 13 10 21 20 32 30 46 40 64 50 85 60 110 (Total for Question 4 = 2 marks)
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(2)Calculate
A saturated solution of potassium nitrate in 100 g of water at 50 °C is cooled to 20 °C. Calculate the mass of crystals that forms.
Figure 1 — the solubility of potassium nitrate in water at different temperatures. Plotted as a line; the graph is drawn in Incandio and the readings are below. Temperature / °C Solubility / g per 100 g of water 0 13 10 21 20 32 30 46 40 64 50 85 60 110 ............................ g
(Total for Question 5 = 2 marks)
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(4)Describe
Describe how you would find the solubility of a salt in water at 25 °C.
(Total for Question 6 = 4 marks)
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(2)Explain
Explain why a saturated solution left in an open dish at constant temperature slowly produces crystals.
(Total for Question 7 = 2 marks)
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(2)Suggest
Suggest why a solubility curve for a gas dissolved in water slopes downwards as temperature increases.
(Total for Question 8 = 2 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 — 11 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain Solubility and Solubility Curves to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Joseph Louis Gay-Lussac over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Solubility and Solubility Curves — Why a solution can be full, why hot water holds more, and how one curve tells you exactly how many crystals you will get back.
- All of Incandio Chemistry · Incandio Exam Practice