Crude composition baseline: Approximately what fraction by weight of hydrogen does typical crude petroleum contain?

Introduction:
Crude oil is a complex mixture of hydrocarbons with minor heteroatoms (S, N, O, metals). The overall hydrogen-to-carbon balance drives energy content, emissions, and processing severity. This question asks for a representative hydrogen mass percentage in typical crude oils.

Given Data / Assumptions:

• We consider conventional crudes (excluding extreme bitumen or ultra-light condensates).
• Industry references commonly cite hydrogen around the mid-teens by weight.

Concept / Approach:
Most crudes show about 83–87% carbon and 11–14% hydrogen by weight, with the remainder being heteroatoms. A rounded representative value is about 15%, which aligns with exam conventions and captures lighter crudes on the higher end of hydrogen content.

Step-by-Step Solution:

Verification / Alternative check:
Crude assay summaries consistently report hydrogen near the mid-teens by weight, with variation tied to paraffinic versus aromatic content.

Why Other Options Are Wrong:

• 5: Too low for crude hydrocarbons.
• 25 or 35 or 45: Far above realistic hydrogen mass fractions in crude.

Common Pitfalls:
Confusing atomic percent with mass percent; by mass, hydrogen is a minority component.

Final Answer:
15