Fuel composition: For the following fuels, which has the highest carbon-to-hydrogen ratio by weight—gasoline, kerosene, light gas oil, or heavy fuel oil?

Introduction / Context:
Carbon/hydrogen (C/H) ratio by weight is a useful indicator of fuel heaviness and combustion characteristics. As hydrocarbon chains become heavier and more aromatic, the C/H ratio typically increases, affecting energy content, smoke tendency, and emissions.

Given Data / Assumptions:

• We compare typical petroleum products: gasoline, kerosene, light gas oil (LGO), and heavy fuel oil (HFO).
• We assume conventional refinery specifications without unusual additives.
• C/H ratio is by weight.

Concept / Approach:
Lighter distillates (gasoline, kerosene) have higher hydrogen-to-carbon relative content and more paraffinic composition. As products get heavier (LGO → HFO), average molecular weight increases, aromaticity often rises, and the hydrogen fraction drops, raising the C/H ratio.

Step-by-Step Solution:

Verification / Alternative check:
Elemental analyses of refinery streams consistently show heavier residual fuels with lower hydrogen content (by wt%), hence higher C/H ratios than lighter distillates.

Why Other Options Are Wrong:

• Light gas oil: Heavier than kerosene/gasoline but lighter than HFO; C/H lower than HFO.
• Kerosene: Mid-distillate with higher hydrogen fraction than LGO/HFO.
• Gasoline: Lightest among the four; typically the lowest C/H ratio.

Common Pitfalls:
Confusing H/C atomic ratio with C/H weight ratio; regardless of expression, heavier residual fuels have relatively less hydrogen.

Final Answer:
Heavy fuel oil