Hydrogen-to-carbon balance: For hydrocarbons with the same carbon number, which family has the highest hydrogen-to-carbon ratio by weight?

Introduction / Context:
The hydrogen-to-carbon (H/C) ratio influences combustion cleanliness, smoke tendency, and product properties. For a fixed carbon number, more saturation generally means higher hydrogen content.

Given Data / Assumptions:

• Families: paraffins (saturated acyclic), naphthenes (cycloalkanes), olefins (alkenes), and aromatics.
• Comparison at equal carbon count.
• Basis: weight ratio.

Concept / Approach:
Paraffins are fully saturated (CnH2n+2) with the maximum hydrogen content for a given n. Cyclization or unsaturation reduces hydrogen count (to CnH2n for naphthenes and olefins). Aromatics have even lower H/C due to ring unsaturation.

Step-by-Step Solution:

Verification / Alternative check:
Elemental analyses confirm higher hydrogen wt% for paraffins versus cyclic/unsaturated counterparts at the same n.

Why Other Options Are Wrong:

• Naphthenes / Olefins: Each has fewer hydrogens than paraffins for the same n.
• Aromatics: Lowest H/C among the listed families.

Common Pitfalls:
Mixing atomic and weight ratios; the ordering remains the same for typical carbon numbers.

Final Answer:
Paraffins