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

Options

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

Answer

To analyze the reaction \( \text{CuSO}_4 + 2\text{KCN} \rightarrow \text{CuCN} \downarrow + \text{CN}_2 \uparrow + \text{K}_2\text{SO}_4 \), we need to determine the type of reaction it represents. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Reactants and Products
The reactants in this reaction are:
- Copper(II) sulfate (\( \text{CuSO}_4 \))
- Potassium cyanide (\( \text{KCN} \))

The products formed are:
- Copper(I) cyanide (\( \text{CuCN} \))
- Dicyan (gas, \( \text{CN}_2 \))
- Potassium sulfate (\( \text{K}_2\text{SO}_4 \))

### Step 2: Analyze the Products
In the products, we observe:
- \( \text{CuCN} \) is indicated with a downward arrow (\( \downarrow \)), which signifies that it is a precipitate.
- \( \text{CN}_2 \) is indicated with an upward arrow (\( \uparrow \)), which signifies that it is a gas.

### Step 3: Determine the Type of Reaction
To classify the reaction, we consider the following:
- A **precipitate formation reaction** occurs when a solid (precipitate) is formed from the reaction of two solutions.
- A **precipitate dissolution reaction** occurs when a solid (precipitate) dissolves into its ions in solution.
- A **precipitate exchange reaction** involves the exchange of ions between two compounds, leading to the formation of a precipitate.
- **No reaction** implies that the reactants do not produce any new products.

Since we have a solid precipitate (\( \text{CuCN} \)) forming in the products and no precipitate in the reactants, this indicates that a new solid has formed from the reaction.

### Conclusion
Thus, the reaction is classified as a **precipitate formation reaction**.

### Final Answer
The answer is: **A. Precipitate formation reaction.**

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