Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed
Reversible Reactions — exam questions
12 original Incandio exam-style questions on Reversible Reactions, 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 Reversible Reactions — 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
- Name (1 mark)
- the correct chemical name
- 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
- 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 3.17 · 3.18. 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 heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(a)
(1)Give
Give the colour change seen when the student first heated the crystals.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(b)
(2)Describe
Describe what happened when the liquid was added back to the white solid, and what it shows.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(c)
(3)Explain
Explain what the two experiments in the stimulus have in common, in terms of how the direction of each reaction is controlled.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(d)
(3)Suggest
Suggest why the ammonium chloride experiment could never reach a point where nothing further happened, if the tube were sealed and kept at one temperature throughout.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(Total for Question 1 = 9 marks)
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(1)Which
Which symbol is used in an equation for a reversible reaction?
Symbol A → B ⇌ C = D + (Total for Question 2 = 1 mark)
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(1)Give
Give the colour of anhydrous copper(II) sulfate.
(Total for Question 3 = 1 mark)
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(1)Name
Name the colourless liquid that collected at the top of the tube.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(Total for Question 4 = 1 mark)
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(2)Describe
Describe what is meant by a reversible reaction.
(Total for Question 5 = 2 marks)
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(3)Explain
Explain why the tube became warm when water was added to the white solid.
A student heated blue hydrated copper(II) sulfate crystals in a test tube. The crystals turned white and droplets of a colourless liquid collected at the cool top of the tube. She let the tube cool, then added a few drops of that liquid back to the white solid. The solid turned blue again and the tube became noticeably warm.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(Total for Question 6 = 3 marks)
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(2)Explain
Explain why the white solid in the ammonium chloride experiment appears on the cooler part of the tube.
A second reversible reaction — Ammonium chloride, NH₄Cl, breaks down on heating into ammonia and hydrogen chloride, which recombine to form a white solid on the cooler part of the tube: NH₄Cl ⇌ NH₃ + HCl
(Total for Question 7 = 2 marks)
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(3)Suggest
Suggest why burning magnesium in oxygen is not written as a reversible reaction.
Burning magnesium — 2Mg + O₂ → 2MgO, ΔH = −1204 kJ per mole of oxygen. Magnesium oxide left in air for years shows no change, and industrial magnesium is obtained from its compounds by electrolysis.
(Total for Question 8 = 3 marks)
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(4)Explain
Blue hydrated copper(II) sulfate turns white when heated, and the white solid turns blue again when water is added. Explain what this shows about the reaction and how it could be used as a test.
(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 Reversible Reactions to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Joseph Black over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Reversible Reactions — Reactions that run both ways, and two you can drive backwards and forwards at will.
- All of Incandio Chemistry · Incandio Exam Practice