Name three gases which are used in warfare as posionous gases and prepared by chlorine.

Explanation

To answer the question about three gases used in warfare as poisonous gases and prepared from chlorine, we can follow these steps:

### Step 1: Identify the Gases
We need to identify three poisonous gases that are prepared using chlorine.

### Step 2: List the Gases
1. **Phosgene (COCl2)**:
- Phosgene is a highly toxic gas that is prepared by passing carbon monoxide (CO) and chlorine (Cl2) through a bed of porous activated carbon, which acts as a catalyst.
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