Question detail
Which of the following best illustrates the energy change during hydrocarbon combustion?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Carbon compounds as fuels and feedstock
Question
- A. Energy is absorbed from the surroundings to break C–H bonds.
- B. Energy is released when new C=O and O–H bonds form.
- C. Energy is stored in the hydrocarbon and released as light only.
- D. Energy is transferred to the oxygen molecules, raising their temperature.
Answer
The correct option is Energy is released when new C=O and O–H bonds form..
Explanation
The correct option is Energy is released when new C=O and O–H bonds form.. Energy is released when new C=O and O–H bonds form. is correct because it directly supports the approved learning objective to explain that combustion of hydrocarbon fuels releases energy. This belongs to Properties and combustion of hydrocarbons within Carbon compounds as fuels and feedstock, so the answer must use the correct organic chemistry context. The other options are incorrect when they confuse the organic family, formula type, reaction condition, product, or property being tested. Keep molecular formula, structural formula, displayed formula, and general formula distinct. Do not confuse alkanes with alkenes, saturated with unsaturated, cracking with combustion, polymers with monomers, or hydrocarbons with oxygen-containing alcohols and carboxylic acids. When formulae are used, preserve the stored notation exactly and explain the GCSE chemistry idea in words rather than using unsupported displayed-formula diagrams.
Common mistake
Energy release misattributed to oxidation of hydrogen
Students often think that the energy released in hydrocarbon combustion comes mainly from the oxidation of hydrogen atoms rather than the oxidation of carbon atoms.
Explain that while both carbon and hydrogen are oxidised, the large amount of energy released comes from the formation of strong C–O and O–O bonds when carbon is oxidised to CO₂; the oxidation of hydrogen to H₂O also releases energy but contributes less to the total energy change.
Related flashcards
Flashcard 1 of 5
Related practice questions
Question 1 of 5
Choose an answer, get feedback, then move sideways through the set.