Write the chemical test to identify the following gases.
`O_2`

Explanation

To identify the gas \( O_2 \) (oxygen), we can use the following chemical test:

### Step-by-Step Solution:

1. **Prepare an Alkaline Solution of Pyrogallol**:
- Pyrogallol, also known as 1,2,3-trihydroxybenzene, is a weak acid with the chemical formula \( C_6H_6O_3 \).
- To prepare the alkaline solution, dissolve pyrogallol in water and add a suitable alkali, such as sodium hydroxide (NaOH).

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