How many moles of KCN are required to convert 1 mole of `CuSO_(4)` to `[Cu(CN)_(4)]^(-3)`?

Answer

To determine how many moles of KCN are required to convert 1 mole of CuSO₄ to [Cu(CN)₄]³⁻, we can follow these steps:

### Step 1: Write the reaction of CuSO₄ with KCN
When copper(II) sulfate (CuSO₄) reacts with potassium cyanide (KCN), it first forms copper(I) cyanide complex. The balanced reaction is:
\[ \text{CuSO}_4 + 2 \text{KCN} \rightarrow \text{Cu(CN)}_2 + \text{K}_2\text{SO}_4 \]

### Step 2: Identify the product
The product formed is copper(I) cyanide (Cu(CN)₂), which is unstable and can dissociate into:
\[ 2 \text{Cu(CN)}_2 \rightarrow 2 \text{Cu} + 2 \text{CN} \]

### Step 3: React Cu(CN)₂ with KCN
Now, the copper(I) cyanide (Cu(CN)₂) can react with additional KCN to form the tetra-cyanide complex:
\[ \text{Cu(CN)}_2 + 3 \text{KCN} \rightarrow \text{K}_3\text{Cu(CN)}_4 \]

### Step 4: Calculate total moles of KCN
From the reactions:
- The first reaction requires 2 moles of KCN.
- The second reaction requires 3 moles of KCN.

Adding these together gives:
\[ 2 \text{ moles of KCN} + 3 \text{ moles of KCN} = 5 \text{ moles of KCN} \]

### Conclusion
Thus, to convert 1 mole of CuSO₄ to [Cu(CN)₄]³⁻, **5 moles of KCN are required**.

---