`SO_2` is considered as an air pollutant because

Options

A. Its concentration increases with temperature increases of atmosphere.
B. It is used as an insecticide which is air pollutant
C. It reacts with `O_2 and H_2O` to produce acid rain
D. It is a strong oxidant and oxidant oxidizes other components of atmosphere

Answer

To solve the problem regarding the reaction of `SO2` and `O2` to form `SO3`, we will follow these steps:

### Step-by-Step Solution:

1. **Write the Balanced Chemical Equation**:
The balanced equation for the reaction is:
\[ 2 \text{SO}_2 + \text{O}_2 \rightarrow 2 \text{SO}_3 \]

2. **Identify Initial Volumes**:
We are given:
- Volume of `SO2` = 5 liters
- Volume of `O2` = 3 liters

3. **Determine the Stoichiometric Ratios**:
From the balanced equation, we see that:
- 2 volumes of `SO2` react with 1 volume of `O2`.
- Therefore, 5 liters of `SO2` would require:
\[ \text{Required } O_2 = \frac{5 \text{ liters } SO_2}{2} = 2.5 \text{ liters } O_2 \]

4. **Identify the Limiting Reagent**:
Since we have 3 liters of `O2` available and only 2.5 liters are needed for the reaction with 5 liters of `SO2`, `SO2` is the limiting reagent.

5. **Calculate Final Volumes**:
- **For `SO2`**: It will be completely consumed, so the final volume of `SO2` = 0 liters.
- **For `O2`**: The amount of `O2` that reacts is 2.5 liters, so the remaining volume of `O2` is:
\[ 3 \text{ liters } O_2 - 2.5 \text{ liters } O_2 = 0.5 \text{ liters } O_2 \]
- **For `SO3`**: According to the stoichiometry of the reaction, 2 liters of `SO2` produce 2 liters of `SO3`. Thus, 5 liters of `SO2` will produce:
\[ 5 \text{ liters } SO_3 \]

6. **Calculate Total Final Volume**:
The total final volume of the reaction mixture is the sum of the volumes of the products and the unreacted reactants:
\[ \text{Total Volume} = \text{Volume of } SO_3 + \text{Remaining } O_2 + \text{Remaining } SO_2 \]
\[ = 5 \text{ liters } SO_3 + 0.5 \text{ liters } O_2 + 0 \text{ liters } SO_2 = 5.5 \text{ liters} \]

### Final Answer:
The volume of the reaction mixture at the completion of the reaction is **5.5 liters**.

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