Give an example of hydrated salt which is
efflorescent

Explanation

To answer the question, "Give an example of a hydrated salt which is efflorescent," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hydrated Salts**:
- Hydrated salts are salts that contain water molecules within their crystalline structure. These water molecules are known as water of crystallization.

2. **Identifying Efflorescent Substances**:
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