Which of the following ion has the highest coagulation power for the sol. Which is obtained by the following reaction?
`FeCl_(3)("excess")+NaOHtoSol`

Options

A. `Al^(3+)`
B. `SO_(4)^(2-)`
C. `l^(-)`
D. `Na^(+)`

Explanation

To solve the question regarding which ion has the highest coagulation power for the sol obtained from the reaction of FeCl3 with excess NaOH, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction Products**:
The reaction between FeCl3 and NaOH produces ferric hydroxide, which can be represented as:
\[ \text{FeCl}_3 + 3\text{NaOH} \rightarrow \text{Fe(OH)}_3 \downarrow + 3\text{NaCl} \]
Here, Fe(OH)3 is the precipitate formed, and NaCl is a soluble salt.

2. **Determine the Charge of the Colloidal Particles**:
In this reaction, Fe3+ ions are present in excess, leading to the formation of a positively charged colloidal solution (Fe(OH)3).

3. **Understand Coagulation**:
Coagulation is the process of destabilizing a colloidal solution, leading to the aggregation of particles. To coagulate a positively charged sol, we need negatively charged ions.

4. **Identify the Ions in the Options**:
We need to evaluate the coagulation power of the negatively charged ions available in the options. Common negatively charged ions include:
- Sulfate (SO4^2-)
- Iodide (I^-)
- Chloride (Cl^-)
- Nitrate (NO3^-)

5. **Apply Hardy-Schulze Rule**:
According to the Hardy-Schulze rule, the coagulation power of an ion is directly related to its charge. The higher the charge of the ion, the greater its coagulation power.

6. **Compare the Charges**:
- Sulfate (SO4^2-) has a charge of -2.
- Iodide (I^-) has a charge of -1.
- Chloride (Cl^-) has a charge of -1.
- Nitrate (NO3^-) has a charge of -1.

7. **Conclusion**:
Among the negatively charged ions, sulfate (SO4^2-) has the highest charge (-2), which means it has the highest coagulation power for the positively charged Fe3+ ions in the colloidal solution.

### Final Answer:
The ion with the highest coagulation power for the sol obtained from the reaction is **sulfate ion (SO4^2-)**.

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