Problem 35 - A Complete Resource Book in Chemistry for JEE Main

Question

Freon- 12 is commonly used as (a) refrigerant (b) a solvent (c) insecticide (d) a fire extinguisher

Step-by-Step Solution

Answer

Freon-12 is commonly used as (a) refrigerant.

Step 1: Identify Function of Freon-12

Freon-12, also known as dichlorodifluoromethane or CFC-12, is chiefly used in various industries and applications. Originally, it was used in air conditioning systems, which indicates its primary function.

Step 2: Evaluate Options

Let's evaluate each option in the context of Freon-12: (a) Refrigerant: Freon-12 is primarily known as a refrigerant. (b) Solvent: Freon-12 is not primarily classified as a solvent. (c) Insecticide: Freon-12 does not serve this function. (d) Fire extinguisher: Freon-12 is not generally used for these purposes, although some variants of Freon were previously used in fire extinguishing systems.

Step 3: Select the Correct Option

Based on the evaluation: - (a) refrigerant is the correct function of Freon-12. It was widely used in refrigeration and air conditioning systems before environmentally safer alternatives were introduced.

Key Concepts

Refrigerant

Refrigerants are substances used in cooling mechanisms, such as air conditioners and refrigerators. These chemicals work by changing from a gas to a liquid and back again, absorbing and releasing heat in the process.

• In air conditioning, refrigerants absorb heat from the indoor environment and release it outside, cooling the air inside a building.
• Refrigerators use refrigerants in a similar process to keep food and beverages cool and fresh.

Freon-12 has been one of the most popular refrigerants. However, due to its environmental impact, its use has been reduced in favor of alternatives that pose less risk to the ozone layer.

Dichlorodifluoromethane

Dichlorodifluoromethane is a chemical compound with the formula \(\text{CCl}_2\text{F}_2\). It is a type of chlorofluorocarbon (CFC).

• This compound was once the standard in refrigeration and air conditioning systems due to its stability and nonflammability.
• Dichlorodifluoromethane is colorless and has a slight ethereal smell.

The name "dichlorodifluoromethane" comes from its chemical structure, involving two chloride (Cl) and two fluoride (F) atoms bonded to a single methane (CH) group.

CFC-12

CFC-12 is a shorthand name for dichlorodifluoromethane, highlighting its identity as a chlorofluorocarbon.

• CFCs, including CFC-12, have been used not only as refrigerants but also as propellants in aerosol cans and for foam blowing.
• They have been popular due to their stability, but this very feature makes them persist in the atmosphere.
• With increasing awareness of environmental issues, the production and use of CFC-12 have been curtailed under international agreements.

Today, industries are moving towards more eco-friendly refrigerants to replace CFC-12, reducing harm to the environment.

Environmental Impact of CFCs

CFCs, like CFC-12, have significant negative effects on the environment. Their stability allows them to reach the stratosphere unchanged, where they break down and release chlorine atoms.

• These chlorine atoms contribute to the depletion of the ozone layer, which protects Earth from harmful ultraviolet radiation.
• A thinner ozone layer leads to increased UV exposure, which can cause skin cancer, cataracts, and other health problems in humans, as well as affecting animals and plants.
• The Montreal Protocol was established to phase out the production and use of ozone-depleting substances, including CFCs.

Since the adoption of this protocol, the use of CFCs has decreased rapidly, showing a significant step towards environmental conservation and safety.