In atmosphere, `SO_(2)` and `NO` are oxidised to `SO_(3)` and `NO_(2)`, respectively,w hcih react with water to given `H_(2)SO_(4)` and `HNO_(3)`. The resultant solution is called acid rain. `SO_(2)`dissolves in water to form diprotic acid.
`SO_(2)(g) +H_(2)O(l) hArr HSO_(3)^(Theta) + H^(o+), K_(a_(1)) = 10^(-2)`.
`HSO_(3)^(Theta) hArr SO_(3)^(2-) + H^(o+), K_(a_(2)) = 10^(-7)`
and for equilibrium,
`SO_(2)(aq) + H_(2)O (l) hArr SO_(3)^(2-)(aq) +2H^(o+)(aq)`
`K_(a) = K_(a_(1)) xx K_(a_(2)) = 10^(-9) at 300K`.
Which of the following statement is correct?

Options

A. `H_(2)SO_(3)` is less acidic than `H_(2)SO_(4)`.
B. `HNO_(3)` is less acidic than `HNO_(2)`.
C. `SO_(2)(g)` is reduced in the atmosphere during thunderstron.
D. `CO_(2)` gas develop more acidity in rain water than `SO_(2)`.

Answer

To solve the question regarding the acidity of different acids and the behavior of sulfur dioxide (SO₂) in the atmosphere, we need to analyze the statements provided and determine which ones are correct based on the information given in the problem.

### Step-by-Step Solution:

1. **Understanding the Acids Involved:**
- The question mentions sulfurous acid (H₂SO₃) and sulfuric acid (H₂SO₄). We know that sulfuric acid has a higher oxidation state of sulfur compared to sulfurous acid, which generally makes it a stronger acid due to the presence of more oxygen atoms.

2. **Analyzing Statement 1:**
- **Statement:** H₂SO₃ is less acidic than H₂SO₄.
- **Analysis:** This statement is correct because H₂SO₄ has more oxygen atoms, which increases its ability to donate protons (H⁺ ions) compared to H₂SO₃. Therefore, H₂SO₃ is indeed less acidic than H₂SO₄.

3. **Analyzing Statement 2:**
- **Statement:** HNO₃ is less acidic than HNO₂.
- **Analysis:** This statement is incorrect. HNO₃ (nitric acid) is a stronger acid than HNO₂ (nitrous acid) because it has a higher oxidation state of nitrogen and more oxygen atoms, which stabilize the negative charge after deprotonation.

4. **Analyzing Statement 3:**
- **Statement:** SO₂ gas is reduced in the atmosphere during thunderstorms.
- **Analysis:** This statement is incorrect. The problem states that SO₂ is oxidized to SO₃ in the atmosphere, particularly during thunderstorms. Therefore, SO₂ is not being reduced.

5. **Analyzing Statement 4:**
- **Statement:** CO₂ gas develops more acidity in rainwater than SO₂.
- **Analysis:** This statement is correct. While both CO₂ and SO₂ can contribute to acidity in rainwater, SO₂ leads to the formation of sulfurous acid (H₂SO₃), which is less acidic than the carbonic acid (H₂CO₃) formed from CO₂. However, the overall contribution of SO₂ to acid rain is significant due to its conversion to stronger acids like H₂SO₄.

6. **Conclusion:**
- The correct statements are:
- Statement 1: H₂SO₃ is less acidic than H₂SO₄ (Correct).
- Statement 4: CO₂ gas develops more acidity in rainwater than SO₂ (Correct).
- Therefore, the correct options are A and D.