Fractional Distillation Separates Petroleum by Boiling Point

Steps:

• In a fractionating column, heat causes hydrocarbons to vaporize; vapors rise and condense at different heights based on boiling points.
• Lighter, shorter-chain hydrocarbons have lower boiling points and higher volatility, collecting at the top.
• Heavier, longer-chain hydrocarbons have higher boiling points and lower volatility, collecting at the bottom.
• Evaluate statements: 1 matches volatility and boiling point trends; 2 misattributes viscosity to chain length phrasing and ignores longer bottom chains being more viscous; 3 reverses chain length distribution.

Why B is correct:

• Statement 1 aligns with the principle of fractional distillation, where separation occurs due to differences in boiling points (lower at top for volatile compounds).

Why the others are wrong:

• A includes incorrect statements 2 and 3 on viscosity and chain length.
• C includes incorrect statement 3, as bottom molecules have longer chains.
• D includes both incorrect statements 2 and 3.

Final answer: B