`HgI_(2)darr+KI hArrK_(2)[HgI_(4)]`

Options

A. For precipitate formation reaction
B. For precipitate dissolution reaction
C. For precipitate exchange reaction
D. For no reaction

Answer

To solve the question regarding the reaction of \( \text{HgI}_2 \) with \( \text{KI} \) to form \( \text{K}_2[\text{HgI}_4] \), we need to analyze the nature of the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are \( \text{HgI}_2 \) (mercury(II) iodide) and \( \text{KI} \) (potassium iodide).
- The product formed is \( \text{K}_2[\text{HgI}_4] \) (potassium tetraiodomercurate(II)).

2. **Understand the Reaction Type**:
- The downward arrow in the equation indicates that \( \text{HgI}_2 \) is a precipitate. This means that it is in solid form before the reaction occurs.

3. **Analyze the Reaction**:
- When \( \text{HgI}_2 \) reacts with \( \text{KI} \), it forms \( \text{K}_2[\text{HgI}_4] \). The formation of this complex suggests that the solid \( \text{HgI}_2 \) is being converted into a soluble complex.

4. **Determine the Nature of the Reaction**:
- Since \( \text{HgI}_2 \) is a precipitate at the start and is no longer present after the reaction (as it has been converted into the soluble \( \text{K}_2[\text{HgI}_4] \)), we can conclude that the precipitate has dissolved into the solution.

5. **Classify the Reaction**:
- Based on the analysis, this reaction is classified as a **precipitate dissolution reaction**. This is because a precipitate (solid) is present at the reactant side but is no longer present at the product side, indicating that it has dissolved.

### Conclusion:
The correct classification for the reaction \( \text{HgI}_2 + \text{KI} \rightarrow \text{K}_2[\text{HgI}_4] \) is a **precipitate dissolution reaction**.