Problem 9 - A Complete Resource Book in Chemistry for JEE Main

Question

Household fuel (LPG) mainly contains (a) \(\mathrm{CH}_{4}\) (b) \(\mathrm{C}_{2} \mathrm{H}_{2}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{4}\) (d) \(\mathrm{C}_{4} \mathrm{H}_{10}\)

Step-by-Step Solution

Answer

LPG mainly contains butane, which is \\(\mathrm{C}_{4} \mathrm{H}_{10}\\) (option d).

Step 1: Identifying Household Fuel (LPG)

LPG stands for Liquefied Petroleum Gas, which is a common type of household fuel used for cooking and heating.

Step 2: Analyzing Molecular Formulas

Review the molecular formulas provided: - \(\mathrm{CH}_{4}\) is methane.- \(\mathrm{C}_{2} \mathrm{H}_{2}\) is acetylene.- \(\mathrm{C}_{2} \mathrm{H}_{4}\) is ethylene.- \(\mathrm{C}_{4} \mathrm{H}_{10}\) is butane, which is a primary component of LPG.

Step 3: Determining the Composition of LPG

LPG mainly consists of propane \(\mathrm{C}_{3} \mathrm{H}_{8}\) and butane \(\mathrm{C}_{4} \mathrm{H}_{10}\). Since the given options include butane, and not propane, \(\mathrm{C}_{4} \mathrm{H}_{10}\) is the correct choice.

Step 4: Selecting the Correct Option

From the analysis above, we conclude that LPG mainly contains butane \(\mathrm{C}_{4} \mathrm{H}_{10}\). Therefore, option (d) is the correct answer.

Key Concepts

Molecular Formulas

Molecular formulas represent the types and numbers of atoms in a molecule of a substance. For example,

• \( \mathrm{CH}_{4} \) stands for methane, which has one carbon atom and four hydrogen atoms.
• \( \mathrm{C}_{2} \mathrm{H}_{2} \) is acetylene, having two carbon atoms and two hydrogen atoms.
• \( \mathrm{C}_{2} \mathrm{H}_{4} \) represents ethylene, with two carbon and four hydrogen atoms.
• \( \mathrm{C}_{4} \mathrm{H}_{10} \) stands for butane, composed of four carbon atoms and ten hydrogen atoms.

These formulas are useful because they provide a clear and quick representation of the chemical structure. Knowing a molecular formula can help predict the behavior and properties of the substance in chemical reactions.

Chemical Composition of Fuels

When it comes to understanding the chemical composition of fuels such as Liquefied Petroleum Gas (LPG), knowing what's inside helps determine their use and efficiency.
LPG is a mixture that primarily consists of:

• Propane \( \mathrm{C}_{3} \mathrm{H}_{8} \)
• Butane \( \mathrm{C}_{4} \mathrm{H}_{10} \)

These hydrocarbons are gases at standard temperature and pressure, but they are easily liquefied, hence the name. The chemical composition of LPG provides:

• High energy content, which is efficient for cooking and heating.
• Clean combustion, leading to fewer pollutants when burned compared to other fuels.

Understanding the chemical makeup of these fuels allows us to appreciate their effectiveness and their environmental impact.

Hydrocarbons

Hydrocarbons are organic compounds made solely of hydrogen and carbon atoms. They serve as the building blocks for many fuels.
The hydrocarbons like those found in LPG are classified into different types based on their structures:

• Alkanes: Saturated hydrocarbons like methane \( \mathrm{CH}_{4} \) and butane \( \mathrm{C}_{4} \mathrm{H}_{10} \)
• Alkenes: Unsaturated hydrocarbons such as ethylene \( \mathrm{C}_{2} \mathrm{H}_{4} \) that contain at least one double bond.
• Alkynes: Containing triple bonds, such as acetylene \( \mathrm{C}_{2} \mathrm{H}_{2} \)

Hydrocarbons are versatile and crucial to our energy needs. LPG, with its main components being propane and butane, is just one example of how these compounds are utilized to provide energy for everyday tasks. The efficient energy release from hydrocarbons is what makes them incredibly valuable as fuels.