Question detail
What is the general formula for 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. CnH2n+2
- B. CnH2n
- C. CnH2n-2
- D. CnH2n-1
Answer
The correct option is CnH2n.
Explanation
The correct option is CnH2n. CnH2n is correct because it directly supports the approved learning objective to visualise and represent 2D and 3D forms of alkene molecules. (MS 5b). This belongs to Structure and formulae 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
Misunderstanding 2D and 3D representations
Students often confuse 2D representations of alkene molecules with their 3D forms, leading to incorrect visualization of molecular geometry.
Practice drawing both 2D and 3D models of alkene molecules, paying attention to the angles and spatial arrangement of atoms to accurately represent their structure.
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