Presence of ozone in a gas sample may be detected by

Options

A. `H_(2)O_(2)`
B. `SO_(2)`
C. `Hg`
D. KI

Explanation

To detect the presence of ozone (O₃) in a gas sample, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Ozone**: Ozone is a triatomic molecule consisting of three oxygen atoms (O₃). It is known for its distinct properties and reactions, particularly its ability to oxidize other substances.

2. **Choosing the Detection Method**: Among the given options (H₂O₂, S₂O₂, Hg, Ti), we need to identify which one can effectively react with ozone to indicate its presence.

3. **Using Mercury (Hg)**: The correct method to detect ozone is by using mercury (Hg). When ozone is passed through mercury, it undergoes a reaction.

4. **Reaction Mechanism**: The reaction involves ozone splitting into oxygen (O₂) and then reacting with mercury. The overall reaction can be summarized as:
\[ 2Hg + O₃ \rightarrow Hg₂O + O₂ \]
This reaction produces mercury oxide (Hg₂O) and releases oxygen gas.

5. **Observation of Results**: As mercury reacts with ozone, it forms mercury oxide, which leads to a change in the physical state of mercury. Initially, mercury has a certain meniscus in a test tube. Upon the formation of mercury oxide, the meniscus changes due to the consumption of mercury in the reaction.

6. **Conclusion**: The presence of ozone can thus be detected by observing the change in the meniscus of mercury when it reacts with ozone. Therefore, the correct answer to the question is option C, mercury (Hg).