Which of the following is used to prepare `Cl_(2)` gas at room temperature from concentrated HCl ?

Options

A. `MnO_(2)`
B. `H_(2)S`
C. `KMnO_(4)`
D. `Cr_(2)O_(3)`

Explanation

To determine which of the following substances can be used to prepare Cl₂ gas at room temperature from concentrated HCl, we will analyze each option provided:

1. **Identify the options**: The options given are:
- MnO₂
- H₂S
- KMnO₄
- Cr₂O₃

2. **Analyze the reactions**: We need to find out which of these substances reacts with concentrated HCl to produce Cl₂ gas.

3. **Check each option**:
- **MnO₂**: Manganese dioxide does not react with concentrated HCl to produce Cl₂.
- **H₂S**: Hydrogen sulfide does not produce Cl₂ when reacted with concentrated HCl.
- **KMnO₄**: Potassium permanganate reacts with concentrated HCl. The reaction is as follows:
\[ 2 KMnO₄ + 16 HCl \rightarrow 2 KCl + 2 MnCl₂ + 5 Cl₂ + 8 H₂O \]
This reaction produces Cl₂ gas.
- **Cr₂O₃**: Chromium(III) oxide does not yield Cl₂ when reacted with concentrated HCl.

4. **Conclusion**: The only substance that produces Cl₂ gas when reacted with concentrated HCl is **KMnO₄**.

Therefore, the correct answer is **KMnO₄**.