About 20 m above the earth, there is an ozone layer. Which one of the following statement about ozone and ozone layer is true?

Options

A. It is beneficial to us as it stops U.V. radiation
B. Conversion of `O_(3)` to `O_(2)` is an endothermic reaction
C. Ozone has a triatomic linear molecule
D. It is harmful as it stops useful radiation

Answer

To solve the question regarding the ozone layer and its characteristics, we will analyze the statements provided and determine which one is true. Here’s a step-by-step breakdown:

### Step 1: Understand the Ozone Layer
The ozone layer is located in the stratosphere, approximately 20 to 30 kilometers above the Earth's surface. It is composed primarily of ozone (O3) molecules.

**Hint:** Remember the location of the ozone layer and its composition.

### Step 2: Identify the Function of the Ozone Layer
The primary function of the ozone layer is to absorb the majority of the sun's harmful ultraviolet (UV) radiation. This absorption protects living organisms on Earth from potential damage caused by UV rays.

**Hint:** Consider the protective role of the ozone layer against UV radiation.

### Step 3: Evaluate the Statements
Now, we need to evaluate the statements provided in the question:

1. **It blocks harmful UV rays from reaching the Earth.**
- This statement is true as the ozone layer absorbs UV radiation, preventing it from reaching the Earth's surface.

2. **The conversion of O3 to O2 is an endothermic reaction.**
- This statement is false. The conversion of ozone (O3) to oxygen (O2) is an exothermic reaction, meaning it releases heat.

3. **Ozone has a triatomic linear geometry.**
- This statement is false. Ozone has a bent molecular geometry, not linear.

4. **It is harmful as it stops useful radiation.**
- This statement is false. The ozone layer is beneficial because it stops harmful radiation, not useful radiation.

### Step 4: Conclusion
Based on the evaluation of the statements, the correct statement about the ozone layer is that it blocks harmful UV rays from reaching the Earth.

**Final Answer:** The true statement is: "It blocks harmful UV rays from reaching the Earth."

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