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

Question

Match the following: List I List II (Petroleum fractions) \(\quad\) (Approximate composition) 1\. gasoline (i) \(\mathrm{C}_{10}\) to \(\mathrm{C}_{15}\) 2\. kerosene (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: 1 \(\begin{array}{lll}2 & 3 & 4\end{array}\) (a) (ii) (i) (iii) (iv) (b) (i) (iii) (iv) (ii) (c) (i) (ii) (iv) (iii) (d) (ii) (i) (iv) (iii)

Step-by-Step Solution

Answer

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

Step 1: Understand the composition ranges

Before matching, it's crucial to understand what each range indicates. The ranges refer to the number of carbon atoms in the hydrocarbon chain. Smaller numbers usually correspond to lighter fractions like gasoline, whereas larger numbers indicate heavier fractions like lubricating oil or pitch and asphalt.

Step 2: Analyze gasoline's composition

Gasoline typically consists of hydrocarbon chains from 6 to 8 carbon atoms, making it the lightest and most volatile of the listed fractions. Therefore, it corresponds to (ii).

Step 3: Analyze kerosene's composition

Kerosene is usually in the range of 10 to 15 carbon atoms ( 10 to 15), which makes it heavier than gasoline but lighter than lubricating oil. Thus, it matches with (i).

Step 4: Analyze lubricating oil's composition

Lubricating oil has longer chains than kerosene, generally around 17 to 20 carbon atoms. So, it corresponds to (iv).

Step 5: Analyze pitch and asphalt's composition

Pitch and asphalt are characterized by very long hydrocarbon chains, usually consisting of 30 to 40 carbon atoms, making them the heaviest fractions. Therefore, they match with (iii).

Step 6: Match List I with List II

Now that we have identified which carbon composition matches with each petroleum fraction, we can write: 1. Gasoline - (ii), 2. Kerosene - (i), 3. Lubricating oil - (iv), 4. Pitch and asphalt - (iii). This corresponds to option (d).

Key Concepts

Hydrocarbon Chains

In the world of chemistry, hydrocarbons are simple organic compounds that consist of hydrogen and carbon atoms. These chains can vary in length, affecting the physical and chemical properties of the compounds. The number of carbon atoms in a hydrocarbon chain determines its weight, boiling point, and usage in various applications.

For instance, shorter chains like those found in gasoline (C6 to C8) are lighter and more volatile, compared to longer chains in lubricating oils or even asphalt, which are heavier and less volatile. Hydrocarbon chains are crucial in determining how we utilize different petroleum fractions.

• Shorter chains: More volatile, used as fuels like gasoline.
• Medium chains: Used in kerosene for heating and lighting.
• Longer chains: Found in lubricants, providing smoothness to machines.
• Very long chains: Used in heavy-duty applications like roads and roofing.

Understanding these differences helps in matching petroleum fractions to their appropriate uses effectively.

Gasoline Composition

Gasoline is a widely used fuel, primarily for powering internal combustion engines in vehicles. This volatile petroleum fraction is notable for its shorter hydrocarbon chains, specifically ranging from C6 to C8 carbon atoms. These shorter chains make gasoline highly flammable and efficient as a rapid source of energy.

The volatile nature of gasoline means it evaporates easily, providing the necessary fumes that engines require to start and run smoothly. Another key aspect is its ability to combust quickly, converting chemical energy into kinetic energy. This is what drives your car forward.

• Consists mainly of C6 to C8 hydrocarbon chains.
• Highly volatile and flammable.
• Efficient quick energy release suitable for engines.

The composition of gasoline is deliberately refined to suit vehicular engine requirements and provide a balance between energy output and emissions.

Kerosene Composition

Kerosene is another important petroleum product, often placed between gasoline and heavier oils in terms of weight and composition. With hydrocarbon chains ranging from C10 to C15, kerosene finds its primary use in heating and lighting.

Compared to gasoline, kerosene is less volatile, making it a safer option for lamps and heaters. This middle-range volatility ensures it burns slower, offering a steady, prolonged heat source. Kerosene's versatility also makes it ideal for jet fuel, where consistent energy output is essential.

• Hydrocarbon chain length: C10 to C15.
• Less volatile than gasoline, safer for use in closed environments.
• Ideal for heating, lighting, and even aviation fuel.

These properties make kerosene a vital component across multiple industries, serving both domestic and commercial needs.

Lubricating Oil Composition

The role of lubricating oil cannot be understated in machinery. Comprising hydrocarbon chains between C17 to C20, lubricating oils are all about reducing friction. These longer chains ensure that the oil can withstand high pressures and temperatures, effectively protecting and prolonging engine life.

The viscosity of lubricating oils allows them to form a protective film over moving parts. This minimizes wear and tear, leading to smoother operation and lowering the need for regular maintenance. They are not only limited to automotive engines but are also used in industrial machinery, ensuring efficient operation.

• Long hydrocarbon chains from C17 to C20.
• High viscosity is ideal for forming protective layers.
• Reduces friction, wear, and tear in machinery.

The unique composition of lubricating oils makes them essential for maintaining smooth mechanical operations across various fields.

Pitch and Asphalt Composition

Pitch and asphalt are some of the heaviest petroleum fractions, noticeable for their incredibly long hydrocarbon chains spanning from C30 to C40. These materials are less about volatility and more about durability and strength.

Primarily used in the construction industry, asphalt serves as a critical component in roads, pavements, and roofing. The high molecular weight of these fractions provides robustness and longevity, capable of withstanding harsh weather conditions and the weight of vehicles.

• Longest hydrocarbon chains: C30 to C40.
• Key use in road construction and roofing materials.
• Offers durability, weather resistance, and load-bearing capabilities.

The strength and resilience of pitch and asphalt come from their composition, helping them serve as foundational materials in infrastructure development.