`Fe(OH)_(3)` when treated with `FeCl_(3)` solution gives a reddish–brown solution. The process involved is:

Options

A. Dispersion
B. Exchange of solvent
C. Peptization
D. None of these

Answer

To solve the question regarding the reddish-brown solution formed when `Fe(OH)_(3)` is treated with `FeCl_(3)`, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding the Initial Components**:
- We start with `Fe(OH)_(3)`, which is a precipitate (PPT) of iron(III) hydroxide. This precipitate is typically large in size, greater than 1000 nm, and does not form a colloid.

2. **Introduction of `FeCl_(3)`**:
- When `FeCl_(3)` is introduced to the `Fe(OH)_(3)` precipitate, it dissociates in solution to provide `Fe^(3+)` ions.

3. **Adsorption of `Fe^(3+)` Ions**:
- The `Fe^(3+)` ions from `FeCl_(3)` will adsorb onto the surface of the `Fe(OH)_(3)` particles. This is due to the common ion effect, where ions of the same type (in this case, `Fe^(3+)`) interact.

4. **Charge Development and Repulsion**:
- As `Fe^(3+)` ions adsorb onto the `Fe(OH)_(3)` particles, they impart a positive charge to the surface of these particles. This leads to electrostatic repulsion between the particles.

5. **Breaking Down the Precipitate**:
- The electrostatic repulsion causes the larger `Fe(OH)_(3)` particles to break down into smaller particles, typically within the range of 1 to 1000 nm, which is the size range for colloidal particles.

6. **Formation of Colloidal Solution**:
- The smaller particles formed are now in the colloidal range and can remain dispersed in the solution, leading to the formation of a reddish-brown colloidal solution.

7. **Conclusion**:
- The entire process is known as **peptization**, where a precipitate is converted into a colloidal solution through the adsorption of ions and subsequent repulsion.

### Final Answer:
The process involved is **peptization**.

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