In a closed container there is a mixture of `SO_(2),CO_(2) and O_(2) ` gas, which sequence of reagent can be helpful to separate them ?
(I) Limewater
(II) Acidified potassium dichromate
(III) Alkaline pyragallol.

Options

A. (I),(II) and (III)
B. (II), (I), (III)
C. (III),(II), (I)
D. (III), (I), (II)

Explanation

To separate the gases SO₂, CO₂, and O₂ from a mixture in a closed container, we can use the following sequence of reagents:

### Step-by-Step Solution:

1. **Use Acidified Potassium Dichromate (K₂Cr₂O₇ + H⁺)**:
- **Reaction**: Acidified potassium dichromate reacts with sulfur dioxide (SO₂) in a redox reaction.
- **Outcome**: SO₂ is absorbed by the potassium dichromate, leaving behind carbon dioxide (CO₂) and oxygen (O₂) in the mixture.
- **Result**: After this step, we have CO₂ and O₂ remaining in the container.

2. **Use Limewater (Calcium Hydroxide, Ca(OH)₂)**:
- **Reaction**: Limewater reacts with carbon dioxide (CO₂) to form calcium carbonate (CaCO₃), which precipitates out.
- **Outcome**: The CO₂ is absorbed by the limewater, leaving only oxygen (O₂) in the container.
- **Result**: After this step, we have O₂ remaining.

3. **Use Alkaline Pyragallol**:
- **Reaction**: Alkaline pyragallol can absorb oxygen (O₂) from the mixture.
- **Outcome**: The O₂ is absorbed by alkaline pyragallol, effectively removing it from the mixture.
- **Result**: After this step, all three gases (SO₂, CO₂, and O₂) have been separated.

### Sequence of Reagents:
- The correct sequence to separate SO₂, CO₂, and O₂ is:
1. Acidified Potassium Dichromate (removes SO₂)
2. Limewater (removes CO₂)
3. Alkaline Pyragallol (removes O₂)

Thus, the correct answer is **Option B: Second, First, Third**.