When mercuric iodide is added to the aqueous solution of potassium iodide, then:

Options

A. freezing point is raised
B. Freezing point is lowered
C. freezing point does not change
D. boiling point does not change

Answer

To solve the question regarding the reaction of mercuric iodide (HgI2) with potassium iodide (KI) in an aqueous solution, we can follow these steps:

### Step 1: Write the Reaction
When mercuric iodide is added to an aqueous solution of potassium iodide, a complex is formed. The reaction can be represented as:
\[ \text{HgI}_2 + 2 \text{KI} \rightarrow \text{K}_2\text{HgI}_4 \]

### Step 2: Identify the Type of Reaction
This reaction involves the formation of a complex, which indicates an association process. In this case, mercuric iodide and potassium iodide associate to form a larger complex ion.

### Step 3: Understand the Impact on Van 't Hoff Factor (i)
The Van 't Hoff factor (i) is a measure of the number of particles the solute breaks into in solution. In this case, since a complex is formed, the effective number of particles in solution decreases. Therefore, the Van 't Hoff factor (i) will decrease.

### Step 4: Relate Van 't Hoff Factor to Freezing Point Depression
The depression in freezing point (\( \Delta T_f \)) is given by the formula:
\[ \Delta T_f = K_f \cdot i \cdot m \]
where \( K_f \) is the freezing point depression constant and \( m \) is the molality of the solution. Since the Van 't Hoff factor (i) decreases due to association, the value of \( \Delta T_f \) will also decrease.

### Step 5: Determine the Effect on Freezing Point
The freezing point of the solution is calculated as:
\[ T_f = T_f^0 - \Delta T_f \]
where \( T_f^0 \) is the freezing point of the pure solvent. If \( \Delta T_f \) decreases, it means that \( T_f \) (the freezing point of the solution) will increase.

### Conclusion
Thus, when mercuric iodide is added to the aqueous solution of potassium iodide, the freezing point of the solution is raised.

### Final Answer
When mercuric iodide is added to the aqueous solution of potassium iodide, the freezing point is raised.

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