Problem 121 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I List II (Petroleum fractions) (Approximate composition) 1\. gasoline (i) \(\mathrm{C}_{10}\) to \(\mathrm{C}_{15}\) 2\. kerosene \(\quad\) (ii) \(\mathrm{C}_{6}\) to \(\mathrm{C}_{8}\) 3\. lubricating oil (iii) \(\mathrm{C}_{30}\) to \(\mathrm{C}_{40}\) 4\. pitch and asphalt (iv) \(\mathrm{C}_{17}\) to \(\mathrm{C}_{20}\) The correct matching is: \(\begin{array}{lll}1 & 2 & 3\end{array}\) 4 (a) (ii) (i) (iii) (iv) (b) (i) (ii) (iv) (ii) \(\begin{array}{llll}\text { (c) (i) } & \text { (ii) } & \text { (iv) (iii) }\end{array}\) (d) (ii) (i) (iv) (iii)

Step-by-Step Solution

Answer

The correct matching is option (d): 1-(ii), 2-(i), 3-(iv), 4-(iii).

Step 1: Understanding the task

We need to match the entries from List I (Petroleum fractions) with entries from List II (Approximate composition). Each fraction in List I has a specific range of carbon atoms in its molecules, given in List II.

Step 2: Analyzing Gasoline

Gasoline is a lighter petroleum fraction typically composed of smaller carbon chains. It usually ranges from \( \mathrm{C}_{6} \) to \( \mathrm{C}_{8} \). Thus, the correct match is (ii).

Step 3: Analyzing Kerosene

Kerosene has intermediate carbon chain lengths within its molecules, generally around \( \mathrm{C}_{10} \) to \( \mathrm{C}_{15} \). Therefore, it matches with (i).

Step 4: Analyzing Lubricating Oil

Lubricating oil consists of longer carbon chains, often ranging from \( \mathrm{C}_{17} \) to \( \mathrm{C}_{20} \). So, it matches with (iv).

Step 5: Analyzing Pitch and Asphalt

Pitch and asphalt are heavy petroleum fractions with very long carbon chains, typically in the range of \( \mathrm{C}_{30} \) to \( \mathrm{C}_{40} \). This range matches with (iii).

Step 6: Determining the Correct Option

Having matched the fractions, the sequences are: 1 with (ii), 2 with (i), 3 with (iv), and 4 with (iii). This matches with option (d).

Key Concepts

Gasoline Composition

Gasoline, a highly volatile fraction of petroleum, is crucial for powering many vehicles. Its composition primarily includes hydrocarbons with carbon atoms ranging from 6 to 8 (\( \mathrm{C}_6 \) to \( \mathrm{C}_8 \)). This makes it less dense and contributes to its high energy content.
The main types of hydrocarbons found in gasoline include:

• Alkanes (or paraffins): These are saturated hydrocarbons and contribute to the stability of gasoline.
• Alkenes (or olefins): They are unsaturated hydrocarbons and provide high-octane ratings, beneficial for engine performance.
• Aromatics: These compounds contain a benzene ring, enhancing the octane rating.

Gasoline formulations are carefully adjusted to ensure performance, with additives such as detergents to clean the engine and antioxidants to prolong fuel shelf life.

Kerosene Composition

Kerosene is a middle-distillate obtained from petroleum refining. It is characterized by its carbon chain length that falls within \( \mathrm{C}_{10} \) to \( \mathrm{C}_{15} \). This makes it heavier than gasoline, but still lighter than diesel and other heavier oils.
Kerosene's composition is vital as it determines its uses in aviation fuel, heating, and lighting.

• Alkanes and cycloalkanes are the predominant hydrocarbon types in kerosene, giving it stability and cost-effectiveness.
• The presence of aromatics is less compared to gasoline, ensuring lower emissions when burned.

Due to its moderate volatility and high flash point, kerosene is ideal for use in jet engines as aviation turbine fuel (ATF). Its low emissions and high energy output make it a clean-burning fuel choice for various non-vehicle applications.

Lubricating Oil Composition

Lubricating oil is essential for reducing wear and friction between mechanical parts. Its molecular structure consists of longer carbon chains, typically between \( \mathrm{C}_{17} \) and \( \mathrm{C}_{20} \). This makes lubricating oil viscous and capable of forming a protective barrier on surfaces.
Key components of lubricating oil include:

• Base oil: Made mainly from refined crude oil, this forms the bulk of lubricating oil.
• Additives: These are added to enhance performance and protect engines, including antioxidants, detergents, and anti-wear agents.

Choosing the right lubricating oil affects machinery efficiency and lifespan. It must withstand high temperatures and pressures while maintaining stability and cleanliness of engine components.

Asphalt Composition

Asphalt, or bitumen, is a dense, viscous petroleum fraction with carbon chain lengths extending from \( \mathrm{C}_{30} \) to \( \mathrm{C}_{40} \). This makes it highly stable and suitable for construction purposes.
Asphalt composition includes:

• Asphaltenes: These are high-molecular-weight compounds contributing to the solid nature of asphalt.
• Maltenes: These are softer components that influence the viscous properties of asphalt.

Due to its durability and water-resistant properties, asphalt is predominantly used in road construction and roofing. Its flexibility allows it to withstand varying weather conditions, making it indispensable in infrastructural applications.