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 \( SO_2 \) (sulfur dioxide), \( CO_2 \) (carbon dioxide), and \( O_2 \) (oxygen) from a mixture in a closed container, we can use the following sequence of reagents:

### Step-by-Step Solution:

1. **Use Acidified Potassium Dichromate**:
- The first reagent we will use is acidified potassium dichromate (\( K_2Cr_2O_7 \)). This reagent selectively absorbs \( SO_2 \) from the mixture.
- **Reaction**: \( SO_2 \) is oxidized by the dichromate, leading to its absorption. After this step, we are left with \( CO_2 \) and \( O_2 \) in the container.

2. **Use Limewater**:
- The next reagent is limewater, which is a solution of calcium hydroxide (\( Ca(OH)_2 \)). Limewater reacts with \( CO_2 \) to form calcium carbonate (\( CaCO_3 \)), which is insoluble and precipitates out.
- **Reaction**: \( CO_2 + Ca(OH)_2 \rightarrow CaCO_3 (s) + H_2O \)
- After this step, we are left with \( O_2 \) gas in the container.

3. **Use Alkaline Pyragallol**:
- The final reagent is alkaline pyragallol, which is a solution that can absorb \( O_2 \).
- **Reaction**: Alkaline pyragallol reacts with \( O_2 \) and absorbs it, leaving no gas in the container.
- After this step, we have successfully separated all three gases.

### Summary of the Sequence:
- The sequence of reagents used is:
1. Acidified Potassium Dichromate (absorbs \( SO_2 \))
2. Limewater (absorbs \( CO_2 \))
3. Alkaline Pyragallol (absorbs \( O_2 \))

### Final Answer:
The correct sequence of reagents to separate \( SO_2 \), \( CO_2 \), and \( O_2 \) is:
**(II) Acidified Potassium Dichromate → (I) Limewater → (III) Alkaline Pyragallol.**

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