Give one use of Alum.

Explanation

**Step-by-Step Solution:**

1. **Definition of Alum**: Alum is a type of chemical compound that is usually a hydrated double sulfate salt of aluminum. Its general formula is represented as \( X \cdot \text{Al}_2(\text{SO}_4)_3 \cdot 12\text{H}_2\text{O} \), where \( X \) is a monovalent cation such as potassium, sodium, or ammonium.

2. **Use of Alum in Water Purification**: One of the primary uses of alum is in water treatment. It acts as a coagulant in the flocculation process, which helps in purifying water. During this process, alum causes impurities and suspended particles in water to clump together and settle down, forming flakes that can be easily removed.

3. **Other Uses of Alum**: Besides water purification, alum has several other applications:
- It is used as a mouth freshener or mouthwash to combat bad breath.
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