Question

Use of chlorofluoro carbons is not encouraged because (a) they are harmful to the eyes of people that use it (b) they damage the refrigerators and air conditioners (c) they eat away the ozone in the atmosphere (d) they destroy the oxygen layer

Short answer

CFCs are not encouraged because they eat away the ozone in the atmosphere (c).

Step-by-step solution

Understand Chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs) are compounds that contain carbon, chlorine, and fluorine. They have been commonly used in refrigeration, air conditioning, packaging, insulation, and aerosol propellants.

Identify Environmental Impact

Despite their applications, CFCs have a significant environmental impact. The most critical impact of CFCs is their role in ozone depletion. When CFCs reach the stratosphere, they release chlorine atoms upon exposure to UV radiation. These chlorine atoms react with ozone ({O_3}), leading to its breakdown.

Evaluate Answer Choices

Analyze each given option: - (a) CFCs being harmful to eyes is not a known concern. - (b) CFCs do not damage the refrigerators and air conditioners they are used in. - (c) CFCs contribute to the depletion of the ozone layer in the atmosphere, known as ozone "eating". - (d) CFCs do not destroy the oxygen layer.

Select the Correct Answer

Based on the analysis, the correct answer is (c) because CFCs are known to cause significant damage to the ozone layer.

Key concepts

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons, commonly known as CFCs, are chemical compounds composed of carbon, chlorine, and fluorine atoms. CFCs have been widely used due to their stability and non-flammability. You'll often find them in applications like:

• Refrigerants in air conditioning and refrigeration systems
• Aerosol propellants in spray cans
• Foam-blowing agents for insulation and packaging materials

Despite their practical uses, CFCs are now heavily regulated due to their environmental impact, specifically their role in ozone layer depletion.

Environmental Impact of CFCs

The environmental impact of CFCs is notable because these chemicals have long atmospheric lifetimes, allowing them to reach the upper layers of the Earth's atmosphere, known as the stratosphere. Upon reaching the stratosphere, CFCs undergo photodissociation, a process initiated by ultraviolet (UV) radiation that breaks down CFC molecules and releases chlorine atoms into the atmosphere. These chlorine atoms then contribute to the depletion of the ozone layer. Thus, CFCs, which seemed harmless at surface level, have proven to be quite damaging to the global environment.

Stratospheric Ozone Layer

The stratospheric ozone layer is a vital component of Earth's atmosphere, situated approximately 10 to 30 miles above Earth's surface. It acts as a shield by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation. The ozone layer is primarily composed of ozone ( O_3 ) molecules. However, when substances such as CFCs enter the stratosphere, they release chlorine atoms that react with ozone. This reaction breaks down the ozone molecules, resulting in holes in the ozone layer. The depletion of this layer poses increased risks to human health and ecosystems globally.

UV Radiation

Ultraviolet (UV) radiation is a type of electromagnetic radiation that comes from the Sun. It is not visible to the human eye but has significant effects on health and the environment. There are three types of UV radiation:

• UVA: Long-wave UV, which penetrates deeply into the skin causing aging and long-term skin damage.
• UVB: Medium-wave UV, which is mostly absorbed by the ozone layer; responsible for sunburn and can lead to skin cancer.
• UVC: Short-wave UV, mostly absorbed by the ozone layer and generally does not reach the Earth’s surface.

The ozone layer plays a crucial role by absorbing the majority of UVB and UVC radiation, protecting life on Earth from these harmful rays.

Chlorine Atoms

Chlorine atoms, once freed from CFCs in the stratosphere, are highly reactive and have the specific ability to destroy ozone (O_3) molecules. The process starts when UV radiation breaks a CFC molecule, releasing a chlorine atom. This chlorine atom can then react with an ozone molecule, resulting in the formation of oxygen (O_2) and a chlorine monoxide (ClO) molecule. The chemical reaction can be summarized as:\[\text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2\]The ClO can further react with another oxygen atom, releasing the chlorine atom back into the atmosphere, where it can continue to destroy more ozone molecules. This catalytic cycle continues, making chlorine atoms a major threat to the ozone layer, as a single chlorine atom can destroy thousands of ozone molecules before being deactivated.