Question

The chemical substance responsible for the depletion of the ozone layer is -

• A. CFC
• B. CO$_2$
• C. DDT
• D. SO$_2$

Hint:

The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion, most notably CFCs.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The ozone layer in the stratosphere protects the Earth from harmful ultraviolet (UV) radiation from the sun.
Certain man-made chemicals can break down ozone molecules, leading to the thinning of this protective layer.

Step 2: Detailed Explanation:
Chlorofluorocarbons (CFCs) are highly stable compounds formerly used in refrigerants and aerosols.
When they reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms.
A single chlorine atom can destroy thousands of ozone (O$_3$) molecules through a catalytic cycle.
While CO$_2$ is a greenhouse gas, DDT is a pesticide, and SO$_2$ causes acid rain, CFCs are the primary culprits for ozone depletion.

Step 3: Final Answer:
The correct option is (A).