Hydrocarbon formulas: Under standard textbook conventions, the general formula CnH2n corresponds to which hydrocarbons?

Difficulty: Easy

Correct Answer: Both olefins (alkenes) and cycloalkanes (naphthenes)

Explanation:


Introduction / Context:
Recognizing empirical formulas helps classify petroleum hydrocarbons and anticipate properties relevant to refining and product performance.


Given Data / Assumptions:

  • Formula: CnH2n with n ≥ 2.
  • Families under consideration: olefins (alkenes) and cycloalkanes (naphthenes).
  • Open-chain versus cyclic structures are both possible.


Concept / Approach:
For saturated open-chain alkanes the formula is CnH2n+2. Introducing one double bond (alkenes) or forming a single ring (cycloalkanes) reduces hydrogen count by two, giving CnH2n. Thus both alkenes and cycloalkanes share CnH2n as their general formula.


Step-by-Step Solution:

Step 1: Recall alkenes: one double bond → CnH2n.Step 2: Recall cycloalkanes: ring formation removes two hydrogens → CnH2n.Step 3: Conclude both families fit the formula.


Verification / Alternative check:
Examples: C6H12 can represent 1-hexene (olefin) or cyclohexane (naphthene), confirming the shared formula.


Why Other Options Are Wrong:

  • Olefins only / Cycloalkanes only: Each excludes the other valid family.
  • Neither: Incorrect because both match.


Common Pitfalls:
Assuming a unique mapping from formula to structure; structural isomerism and rings yield multiple families with the same empirical formula.


Final Answer:
Both olefins (alkenes) and cycloalkanes (naphthenes)

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