During dialysis

Options

A. only solvent molecules can diffuse
B. solvent molecules, ions and colloidal particles can diffuse
C. all kinds of particles can diffuse through the semipermeable membrane
D. solvent molecules and ions can diffuse

Explanation

### Step-by-Step Solution:

1. **Understanding Dialysis**:
- Dialysis is a separation process used to remove dissolved substances or ions from a colloidal solution. It involves the use of a semi-permeable membrane that allows certain particles to pass through while blocking others.

2. **Components of the Dialysis Process**:
- In a typical dialysis setup, you have a colloidal solution containing unwanted ions or small molecules, and you immerse this solution in a solvent (usually water) that acts as the medium for diffusion.

3. **Function of the Semi-Permeable Membrane**:
- The semi-permeable membrane permits the passage of solvent molecules and small ions, but it does not allow larger colloidal particles to pass through. This selective permeability is crucial for the dialysis process.

4. **Diffusion During Dialysis**:
- As the system reaches equilibrium, solvent molecules and small ions will diffuse out of the colloidal solution into the surrounding solvent. Colloidal particles, however, remain trapped within the colloidal solution due to their larger size.

5. **Evaluating the Options**:
- Option A: "Only solvent molecule can diffuse" - This is incorrect because ions can also diffuse.
- Option B: "Solvent molecule, ion, and colloidal particle can diffuse" - This is incorrect because colloidal particles cannot diffuse through the membrane.
- Option C: "All kinds of particles can diffuse" - This is incorrect as not all particles can pass through the membrane.
- Option D: "Solvent molecule and ion can diffuse" - This is correct because both solvent molecules and ions can pass through the semi-permeable membrane, while colloidal particles cannot.

6. **Conclusion**:
- The correct answer is Option D: "Solvent molecule and ion can diffuse."