Which of the following gas in atmosphere is responsible for acidic rain ?

Options

A. CFC
B. `CH_4`
C. `O_3`
D. `SO_2`

Explanation

To determine which gas in the atmosphere is responsible for acid rain, we can follow these steps:

### Step 1: Understand the concept of acid rain
Acid rain is a type of precipitation that has a lower pH than normal rainwater, making it acidic. This acidity is primarily caused by the presence of certain gases in the atmosphere that react with water vapor.

**Hint:** Acid rain is formed when certain gases combine with water vapor in the atmosphere.

### Step 2: Identify the gases responsible for acid rain
The primary gases that contribute to acid rain are sulfur dioxide (SO2) and nitrogen dioxide (NO2). These gases are released into the atmosphere due to various human activities, such as burning fossil fuels.

**Hint:** Look for gases that can form strong acids when they react with water.

### Step 3: Understand the chemical reactions
When sulfur dioxide (SO2) reacts with water vapor, it forms sulfuric acid (H2SO4). Similarly, nitrogen dioxide (NO2) can react with water to form nitric acid (HNO3). Both of these acids are strong acids and contribute to the acidity of rainwater.

**Hint:** Strong acids formed from gas reactions with water lead to acid rain.

### Step 4: Evaluate the options given
1. **CFC (Chlorofluorocarbon)** - These are inert gases and do not contribute to acid rain.
2. **CH4 (Methane)** - This gas does not form strong acids and is not involved in acid rain.
3. **Ozone (O3)** - Ozone exists in the upper atmosphere and does not play a role in acid rain.
4. **SO2 (Sulfur Dioxide)** - This gas is known to form sulfuric acid and is a primary contributor to acid rain.

**Hint:** Eliminate options that do not form strong acids.

### Step 5: Conclusion
Based on the analysis, the gas responsible for acid rain is **SO2 (Sulfur Dioxide)**, as it reacts with water vapor to form sulfuric acid, which is a strong acid.

**Final Answer:** SO2 (Sulfur Dioxide)