Trend across a crude distillation column: From the overhead to the bottom of an atmospheric crude column, which properties show a progressive increase across the product cuts?

Introduction / Context: Fractionation arranges products by volatility. Understanding how key properties vary from the lightest overhead products to the heavy bottoms is foundational to refinery operations and product characterization.

Given Data / Assumptions:

• Standard atmospheric crude distillation (no cracking in the column).
• Products range from gases/naphtha at top to residue at bottom.
• C/H ratio means atomic carbon-to-hydrogen ratio.

Concept / Approach: As we move downward, the average molecular weight increases (heavier molecules), normal boiling points increase, and the carbon-to-hydrogen ratio rises as structures become more aromatic/polynuclear and less hydrogen-rich.

Step-by-Step Solution:

Verification / Alternative check: Assay tables show systematic increases in TBP/ASTM D86 distillation temperatures, density, and Conradson carbon with cut heaviness, consistent with higher MW and C/H.

Why Other Options Are Wrong:

Common Pitfalls: Confusing C/H with H/C; the former increases as streams get heavier and more aromatic.

Final Answer: all (a), (b) and (c)