Pearson Edexcel International GCSE in Chemistry · 4CH1 · Free · no account needed
Energy Diagrams and Bond Energies — exam questions
12 original Incandio exam-style questions on Energy Diagrams and Bond Energies, 27 marks, about 27 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 Energy Diagrams and Bond Energies — 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
7 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 what is meant by (1–2 marks)
- the definition
- 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
- Calculate (1–4 marks)
- a numerical answer with working, to the stated precision
- 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 3.6 · 3.5 · 3.7. 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 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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Hydrogen reacts with chlorine to form hydrogen chloride: H₂ + Cl₂ → 2HCl. One H–H bond and one Cl–Cl bond are broken, and two H–Cl bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 (a)
(1)Calculate
Calculate the total energy needed to break the bonds in the reactants.
Hydrogen reacts with chlorine to form hydrogen chloride: H₂ + Cl₂ → 2HCl. One H–H bond and one Cl–Cl bond are broken, and two H–Cl bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 ............................ kJ
(b)
(2)Calculate
Calculate the total energy released when the bonds in the product are made.
Hydrogen reacts with chlorine to form hydrogen chloride: H₂ + Cl₂ → 2HCl. One H–H bond and one Cl–Cl bond are broken, and two H–Cl bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 total energy released = ............................ kJ
(c)
(3)Calculate
Calculate the overall energy change for the reaction, and state whether it is exothermic or endothermic.
Hydrogen reacts with chlorine to form hydrogen chloride: H₂ + Cl₂ → 2HCl. One H–H bond and one Cl–Cl bond are broken, and two H–Cl bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 (d)
(3)Suggest
Suggest how the energy level diagram for this reaction would differ from one for a reaction with the same ΔH but a much higher activation energy.
Hydrogen reacts with chlorine to form hydrogen chloride: H₂ + Cl₂ → 2HCl. One H–H bond and one Cl–Cl bond are broken, and two H–Cl bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 (Total for Question 1 = 9 marks)
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(1)Which
Which statement about bond breaking is correct?
Statement A it releases energy and is exothermic B it takes in energy and is endothermic C it needs no energy at all D it releases energy and is endothermic (Total for Question 2 = 1 mark)
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(1)State what is meant by
State what is meant by the activation energy of a reaction.
(Total for Question 3 = 1 mark)
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(1)Give
Give the position of the products relative to the reactants on the energy level diagram of an exothermic reaction.
(Total for Question 4 = 1 mark)
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(2)Describe
Describe what an energy level diagram for an endothermic reaction would look like.
(Total for Question 5 = 2 marks)
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(3)Explain
Explain why a reaction is exothermic when more energy is released making bonds than is used breaking them.
(Total for Question 6 = 3 marks)
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(3)Calculate
Calculate the energy change for the reaction 2H₂ + O₂ → 2H₂O, in which two H–H bonds and one O=O bond are broken and four O–H bonds are made.
Table 1 — bond energies Bond Bond energy / kJ per mole H–H 436 Cl–Cl 242 H–Cl 431 O=O 498 O–H 464 energy change = ............................ kJ/mol
(Total for Question 7 = 3 marks)
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(3)Suggest
Suggest why a mixture of hydrogen and oxygen can sit unreacted for years, even though the reaction between them is strongly exothermic.
(Total for Question 8 = 3 marks)
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(4)Explain
Explain why breaking bonds is always endothermic and making bonds is always exothermic, whatever the reaction.
(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 Energy Diagrams and Bond Energies to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against John Dalton over three rounds, marked against descriptors you can read first.
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Back to the lesson
- Energy Diagrams and Bond Energies — Why breaking bonds costs energy, why making them repays it, and why the balance decides everything.
- All of Incandio Chemistry · Incandio Exam Practice