The constituent of petroleum fraction used in surfacing road is

Analysis of the Question

This question tests your knowledge of fractional distillation of petroleum and the specific uses of the various fractions obtained from crude oil. You are asked to identify which specific fraction is used for road construction (surfacing).

Concept Explanation

When crude oil is refined in a refinery, it is separated into different components based on their boiling points. These components are called fractions. Each fraction has a specific use based on its physical properties:

• Petrol (Gasoline): Used primarily as fuel for internal combustion engines (cars).
• Diesel: Used as fuel for heavy-duty vehicles, buses, and generators.
• Lubricating Oil: Used to reduce friction between moving parts of machinery.
• Bitumen (Asphalt): This is the residue left at the bottom of the fractional distillation column. It is a thick, sticky, black substance that is semi-solid at room temperature. Because of its excellent binding and waterproofing properties, it is the standard material used for surfacing roads and roofing.

Step-by-Step Solution

1. Identify the process: The question refers to the products of petroleum refining.
2. Evaluate the options: • A (Petrol) is too volatile and thin for road surfacing. • B (Diesel) is a liquid fuel, not a binding agent. • C (Lubricating oil) is used to reduce friction, not to bind road surfaces. • D (Bitumen) is the heavy, viscous residue specifically processed for road construction and waterproofing.
3. Conclusion: Bitumen is the correct fraction used for road surfacing.

Exam Tip

Think of the "bottom of the barrel." In the fractional distillation tower, the substances with the highest boiling points settle at the bottom. Bitumen is the heaviest fraction, making it the most durable and "sticky" component, which is exactly what you need to hold road stones together!