Question detail
Which of the following formulas would never represent an alkene?
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. C_4H_8
- B. C_3H_6
- C. C_6H_{12}
- D. C_2H_5Cl
Answer
The correct option is C_2H_5Cl.
Explanation
The correct option is C_2H_5Cl. C_2H_5Cl is correct because it directly supports the approved learning objective to state the general formula for the homologous series of alkenes as CnH2n. 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
Confusing Alkene Formula
Students often state the general formula for alkenes incorrectly as CnH2n+2 instead of CnH2n.
Remember that alkenes are unsaturated hydrocarbons with a double bond, which means they have two fewer hydrogen atoms than alkanes, leading to the correct formula CnH2n.
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