Fuels – composition of liquid fuels used in engines and burners Liquid fuels (such as gasoline, diesel, kerosene, and fuel oils) primarily consist of which class of chemical compounds?

Introduction / Context:
Liquid fuels in energy and transportation are largely derived from petroleum. Understanding their chemical makeup is essential for combustion calculations, emissions analysis, and fuel handling. The question asks what class of compounds dominates common liquid fuels.

Given Data / Assumptions:

• Typical fuels: gasoline (petrol), diesel, kerosene, jet fuel, heavy fuel oils.
• Crude oil refining produces mixtures spanning a range of carbon numbers.
• Trace additives (e.g., detergents, oxygenates) may be present but do not change the primary class.

Concept / Approach:

Petroleum-derived liquid fuels are predominantly hydrocarbons—compounds of hydrogen and carbon. Gasoline mainly contains C4–C12 alkanes, cycloalkanes, and aromatics; diesel and kerosene have heavier hydrocarbon fractions (C9–C20+). Oxygenates (e.g., ethanol, MTBE) may be blended, but the fundamental composition remains hydrocarbon-based.

Step-by-Step Solution:

Verification / Alternative check:

Fuel specifications (ASTM, EN) describe hydrocarbon ranges and properties (e.g., cetane number, octane rating), all premised on hydrocarbon chemistry.

Why Other Options Are Wrong:

Carbohydrates / metal oxides: Not fuel bases for petroleum liquids.“True/False” without a statement is ill-posed; the clear correct content is that fuels are hydrocarbons.

Common Pitfalls:

Overemphasizing additives (e.g., ethanol in E10) as the “primary” composition; hydrocarbons remain dominant in most liquid fuel blends.

Final Answer:

They are primarily hydrocarbons