In electrophoresis,

Options

A. the colloidal particles migrate in an applied electric field.
B. the medium migrates in applied electric field
C. both colloidal particles and the medium migrate.
D. neither the particles not the medium migrate.

Answer

**Step-by-Step Solution:**

1. **Understanding Electrophoresis**: Electrophoresis is a process that occurs when an electric field is applied to a colloidal solution. In this process, charged colloidal particles migrate towards the electrode of opposite charge.

2. **Identifying the Movement**: When an electric field is applied, the colloidal particles, which carry a charge, will move towards the electrode that has an opposite charge. For example, negatively charged colloidal particles will move towards the positive electrode (anode), while positively charged particles will move towards the negative electrode (cathode).

3. **Analyzing the Options**: The question provides four options regarding the migration of colloidal particles and the medium in an electric field:
- (A) Colloidal particles migrate in applied electric field.
- (B) The medium migrates in applied electric field.
- (C) Both colloidal particles and the medium migrate.
- (D) Neither the particles nor the medium migrate.

4. **Determining the Correct Statement**: Based on the definition and understanding of electrophoresis, the correct statement is that "colloidal particles migrate in an applied electric field." The medium (solvent) does not migrate in the same way; it remains relatively stationary while the charged particles move.

5. **Conclusion**: Therefore, the correct answer to the question is option (A): "Colloidal particles migrate in an applied electric field."

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