Understanding the Composition of Liquefied Petroleum Gas (LPG)

Liquefied Petroleum Gas, commonly known as LPG, is a flammable mixture of hydrocarbon gases used as fuel in heating appliances, vehicles, and increasingly, in aerosols as a propellant and refrigerant, to replace chlorofluorocarbons.

The composition of LPG can vary, but its main components are typically light hydrocarbons. The most significant components are propane and butane.

• Propane: Chemical formula \(\text{C}_3\text{H}_8\). It's a three-carbon alkane.
• Butane: Chemical formula \(\text{C}_4\text{H}_{10}\). This can exist as two isomers: n-butane and isobutane.

LPG mixtures are often formulated differently depending on the intended use and the climate. For example, in colder climates, a higher proportion of propane is often used because it has a lower boiling point (\(-42^\circ\text{C}\)) than butane (\(-0.5^\circ\text{C}\)), allowing it to vaporize more readily at lower temperatures.

However, the core mixture that defines LPG in general usage and industry standards is the blend of propane and butane.

Analyzing the Options for LPG Composition

Let's look at the given options:

• Option 1: Butane and Isobutane - Isobutane is an isomer of butane, so this option essentially lists different forms of butane. While isobutane is often present in LPG, the primary components are the distinct hydrocarbons propane and butane (including its isomers). This option is not the most complete description of the main mixture.
• Option 2: Propane and Isobutane - This option includes propane and one specific isomer of butane. Again, while accurate that isobutane is part of the butane component, the broader description of LPG focuses on the blend of propane and butane.
• Option 3: Propane and Butane - This option correctly identifies the two primary hydrocarbon gases that form the bulk of typical LPG mixtures. Butane here usually refers to a mix of n-butane and isobutane.
• Option 4: Propane and Tetralin - Tetralin (\(\text{C}_{10}\text{H}_{12}\)) is a bicyclic organic compound, a partially hydrogenated naphthalene. It is definitely not a main component of LPG. LPG consists of light alkanes (propane, butane).

Based on the common definition and composition, LPG is primarily a mixture of propane and butane.

Conclusion on LPG Main Components

The main components that make up Liquefied Petroleum Gas (LPG) are Propane and Butane. These gases are easily liquefied under pressure and stored in cylinders or tanks, making them convenient and portable fuels.

Revision Table: Key LPG Facts

Additional Information: Properties and Uses of LPG

• Properties: LPG is heavier than air. It is odourless, so odorants like ethyl mercaptan are added for safety to detect leaks. It is stored as a liquid under pressure but used as a gas.
• Uses: Widely used for cooking, heating homes and water, as fuel for vehicles (autogas), in agriculture for drying crops, and in various industrial processes.
• Production: LPG is produced during natural gas processing and crude oil refining.