`CuSO_(4)+2KCN to CuCN darr+(CN)_(2)uarr+K_(2)SO_(4)`

Options

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

Answer

To analyze the reaction given in the question, we will break down the steps involved in determining the type of reaction that occurs when copper(II) sulfate reacts with potassium cyanide.

### Step-by-Step Solution:

1. **Identify the Reactants and Products:**
- The reactants are copper(II) sulfate (CuSO₄) and potassium cyanide (KCN).
- The products are copper(I) cyanide (CuCN), cyanogen (CN₂), and potassium sulfate (K₂SO₄).

2. **Write the Balanced Chemical Equation:**
- The balanced equation is:
\[ \text{CuSO}_4 + 2 \text{KCN} \rightarrow \text{CuCN} + \text{CN}_2 + \text{K}_2\text{SO}_4 \]

3. **Determine the Formation of Precipitate:**
- A precipitate is an insoluble solid that forms when two solutions are mixed.
- In this reaction, CuCN is formed, which is a solid precipitate. The downward arrow indicates that it is a precipitate.

4. **Identify the Type of Reaction:**
- Since a precipitate (CuCN) is formed from the reactants (CuSO₄ and KCN), this reaction is classified as a precipitation formation reaction.
- The other options (precipitation dissolution, precipitation exchange, and no reaction) do not apply here because:
- There is no initial precipitate in the reactants.
- There is no dissolution of a solid.
- There is no exchange of precipitates.

5. **Conclusion:**
- The correct classification of the reaction is a precipitation formation reaction.

### Final Answer:
The reaction \( \text{CuSO}_4 + 2 \text{KCN} \rightarrow \text{CuCN} + \text{CN}_2 + \text{K}_2\text{SO}_4 \) is a precipitation formation reaction.