Question detail
Which of the following best describes the combustion of alkenes?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Reactions of alkenes and alcohols (chemistry only)
Question
- A. Always produces carbon dioxide and water
- B. Produces a clear flame
- C. Can produce a smoky flame
- D. Is always complete
Answer
The correct option is Can produce a smoky flame.
Explanation
The correct option is Can produce a smoky flame. Can produce a smoky flame is correct because it directly supports the approved learning objective to explain that alkenes tend to burn in air with smoky flames because of incomplete combustion. This belongs to Reactions of alkenes within Reactions of alkenes and alcohols (chemistry only), 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
Incomplete Combustion Misunderstanding
Students often confuse the reason for smoky flames in alkenes with the presence of impurities in the fuel rather than understanding it is due to incomplete combustion.
Emphasize that smoky flames result from insufficient oxygen during combustion, leading to the production of soot and carbon particles.
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