Which of the following ions has the maximum flocculation value towards coagulation of a positive sol?

Options

A. `[Fe(CN)_(6))]^(4-)`
B. `CI^(-)`
C. `SO_(4)^(2-)`
D. `PO_(4)^(3-)`

Answer

To determine which ion has the maximum flocculation value towards the coagulation of a positive sol, we need to understand the principles of coagulation and flocculation, particularly in relation to the charges of the ions involved.

### Step-by-Step Solution:

1. **Understanding Coagulation and Flocculation**:
- Coagulation is the process where particles in a colloidal solution aggregate to form a precipitate (PPT). Flocculation is similar but refers to the process where the precipitate can be re-dispersed into a colloidal solution upon shaking.
- In this context, we are dealing with a positive sol, which means the dispersed particles carry a positive charge.

2. **Role of Electrolytes**:
- To coagulate a positive sol, we need to introduce anions (negatively charged ions) that can neutralize the positive charge of the sol particles. This neutralization allows the particles to come together and form larger aggregates that can settle out of the solution.

3. **Identifying the Ions**:
- The question provides a set of ions, and we need to evaluate their effectiveness in coagulating a positive sol. According to the Hardy-Schulze rule, the effectiveness of an ion in coagulating a sol is directly related to its charge; higher charged ions are more effective.

4. **Analyzing the Charges**:
- Let's consider the ions typically involved in such questions:
- \( \text{Cl}^- \) (1- charge)
- \( \text{SO}_4^{2-} \) (2- charge)
- \( \text{PO}_4^{3-} \) (3- charge)
- \( \text{SiO}_3^{2-} \) (2- charge)
- According to the Hardy-Schulze rule, the higher the charge of the anion, the more effective it will be in coagulating the positive sol.

5. **Determining Maximum Flocculation Value**:
- Among the ions listed, the \( \text{PO}_4^{3-} \) ion has the highest negative charge (3-). This means it will be the most effective in neutralizing the positive charge of the sol particles, leading to maximum flocculation.

6. **Conclusion**:
- Therefore, the ion with the maximum flocculation value towards the coagulation of a positive sol is \( \text{PO}_4^{3-} \).

### Final Answer:
The ion with the maximum flocculation value towards coagulation of a positive sol is \( \text{PO}_4^{3-} \).