Which of the following processess best describes the purification of muddy water by addition of alum?

Options

A. Adsorption
B. Coagulation
C. Dialysis
D. Electrodialysis

Answer

To solve the question regarding the purification of muddy water by the addition of alum, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding the Composition of Muddy Water**:
- Muddy water contains colloidal particles that are suspended in water. These particles are typically negatively charged, which prevents them from settling due to electrostatic repulsion.

2. **Role of Alum in Purification**:
- Alum (potassium aluminum sulfate) is a coagulant that, when added to muddy water, dissociates into ions. These ions neutralize the negative charges on the colloidal particles.

3. **Coagulation Process**:
- As the negative charges on the colloidal particles are neutralized, the particles lose their repulsive forces. This leads to the aggregation of the particles, allowing them to clump together.

4. **Settling of Aggregated Particles**:
- Once the colloidal particles aggregate, they become heavier and can settle down at the bottom of the container due to gravity. This process is known as sedimentation.

5. **Resulting Purification**:
- After the coagulation and sedimentation processes, the clear water above the settled particles can be decanted, resulting in purified water.

6. **Conclusion**:
- The process that best describes the purification of muddy water by the addition of alum is called **coagulation** or **precipitation**.

### Final Answer:
The purification of muddy water by the addition of alum is best described by the process of **coagulation**.

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