Give the characteristic tests for the following gases:
(i) `CO_(2)` (ii) `SO_(2)` (iii) `O_(2)` (iv) `H_(2)`

Explanation

### Step-by-Step Text Solution:

To identify the characteristic tests for the gases \( \text{CO}_2 \), \( \text{SO}_2 \), \( \text{O}_2 \), and \( \text{H}_2 \), we can perform specific reactions that yield observable results. Here are the tests for each gas:

1. **Carbon Dioxide (\( \text{CO}_2 \))**:
- **Test**: Pass \( \text{CO}_2 \) gas through lime water (calcium hydroxide solution).
- **Observation**: The lime water turns milky.
- **Explanation**: The milky appearance is due to the formation of insoluble calcium carbonate (\( \text{CaCO}_3 \)) when \( \text{CO}_2 \) reacts with calcium hydroxide. The reaction can be represented as:
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