During the fractional distillation of crude oil, the fraction that distills at 200 - 250$^0$ C is

Analysis

This question tests your knowledge of the fractional distillation of crude oil, a core topic in the JAMB Chemistry syllabus. You are required to identify the specific hydrocarbon fraction that vaporizes and is collected within the temperature range of 200°C to 250°C.

Concept Explanation

Crude oil is a mixture of hydrocarbons with different boiling points. During fractional distillation, the crude oil is heated in a fractionating column. As the vapors rise, they cool and condense at different levels based on their boiling points.

Here is the general temperature range for the common fractions:

• Petrol (Gasoline): 40°C – 170°C
• Kerosene (Paraffin): 170°C – 250°C
• Diesel (Gas oil): 250°C – 350°C
• Lubricating oil: 350°C – 400°C
• Bitumen (Residue): Above 400°C

Step-by-Step Solution

1. Evaluate the options: We are looking for the fraction that corresponds to the 200°C – 250°C range.
2. Compare with standard data: • Petrol distills at a lower temperature (below 170°C). • Diesel distills at a higher temperature (starting from 250°C upwards). • Kerosene falls directly within the 170°C – 250°C range.
3. Conclusion: Based on the standard industrial fractional distillation table, the fraction collected between 200°C and 250°C is Kerosene.

Exam Tip

To remember the order of fractions in the column, use the mnemonic: "P-K-D-L-B" (from top to bottom/lowest to highest boiling point):

• Petrol
• Kerosene
• Diesel
• Lubricating oil
• Bitumen

Just remember that as you go down the column, the molecules get larger, the boiling points get higher, and the substances become more viscous (thicker).