Hydrocarbon families – general formula recall Under standard textbook conventions, what is the general formula for naphthenes (cycloalkanes), and how does it relate to olefins?

Introduction / Context:
Recognising family formulas helps in quick classification of petroleum hydrocarbons and in reasoning about properties such as density, reactivity, and hydrogen-to-carbon ratios. Naphthenes (cycloalkanes) often appear in refinery chemistry questions alongside paraffins and olefins.

Given Data / Assumptions:

• Naphthenes are saturated ring compounds (cycloalkanes).
• We compare their general formula to that of olefins.
• Standard classroom conventions apply.

Concept / Approach:
Straight-chain alkanes have formula CnH2n+2. Forming one ring removes two hydrogens relative to the open chain, giving cycloalkanes the formula CnH2n. Olefins (alkenes) also have CnH2n due to one double bond lowering hydrogen count by two. Thus, naphthenes and olefins share the same general formula, even though their structures and properties differ.

Step-by-Step Solution:

Verification / Alternative check:
Examples like cyclohexane (C6H12) and 1-hexene (C6H12) confirm that structural differences can share an empirical formula.

Why Other Options Are Wrong:

• CnH2n+2: Open-chain alkanes (paraffins), not naphthenes.
• CnH2n-6: Typical for monoaromatics such as benzene (n = 6); not cycloalkanes.
• CnHn-4: Not a standard family formula.

Common Pitfalls:
Assuming a unique mapping from formula to structure; many isomers and families can share the same empirical formula.

Final Answer:
CnH2n